Here's where we start getting into more traditional-seeming STEAM activities, which is a little bit of a grumble, because everything in these sequences is expensive to kit out properly or with enough people to be used in a classroom setting. There's a certain belief that you're not doing STEAM if you don't have shiny toys or robots or screens involved. The previous elements have hopefully dispelled that myth, but for places that want to see something visually impressive that they can post on social media or wave in front of funders, the stuff that's in this category is often what they want people to use, and even more so without providing them with the scaffolding or training needed.
That's not a knock against either participants or facilitators. After all, part of the Maker Mentality is being able to throw yourself into something unfamiliar and work out how it works before turning your eyes toward making it do what you want it to, but that takes time and a lot of places are looking for more immediate results, like they are hoping to have one of their participants code up the next Minecraft using library STEAM resources and programs.
So, if yu're going to venture into the world of computing, controlling, robotics, or coding, understand it's going to cost a bit, but many places that cater to the educational market will often have "classroom" kits available that will let you purchase many multiples of something, sometimes with accessories, so that you will have enough on hand. Those places also usually offer tutorials and lessons for learning how to mess around with their devices.
It's equally as likely those tools will have two different types of programming interfaces, so that participants of different ages and skill levels can still get useful time out of the devices. Many of those devices use block-based coding applications and websites, modeled on MIT's Scratch, which is the most prominent one of the lot. There also exists MakeCode for the micro:bit, OzoBlockly for the Ozobot series, and so forth. Many of these block-based editors are based on Google's Blockly library, which allows for a more visual representation of code patterns, and then allows someone to view what the actual code that will be run is related to the placement of those blocks, in whichever langauge is desired. Using block-based coding is a way of overcoming the difficulties of learning and debugging code syntax and having to spend a lot of time hunting for a missed semicolon or an unclosed parenthesis. People who are sufficiently interested after successes with blocks can move on to writing the raw code itself and sending it to be compiled.
That said, most of the tools that are programmable are programmable in ways other than code. Ozobots, for example, have light sensors and have been programmed to recognize certain types of color sequences as requests for the robot to change speed, direction, or to perform one of a set of specific sequences. So even for those who might have trouble constructing block codes can still use the Ozobots to follow lines, change lines, traverse mazes, and the rest. For someone who is artistically inclined, they might want the robot to walk a pathway of art and do things at specific intervals with the color codes embedded in the artwork itself. What they consider success and what we consider success are often different things.
In my ideal world, students and program participants would not be limited solely to what they could experience at the library, but would be able to check out the things they've experienced at the library and then return them, or there would be a foundation or other entity with more money than they knew what to do with such that communities whose libraries are able to acquire interesting tools and use them for programming would also find that there were free kits with that technology available for them to have, without needing to return them unless they wanted to give them to someone else.
It's increasingly clear that having a computer is a necessity in the current era, but so many of the devices we have are wither App Appliances with some other functions bolted on to them or are the single precious item that's necessary for earning a living, and therefore neither of them can be used for learning more generally about the workings of computers and the joys of both breaking and fixing your own computer. Single-board computers like the fruit Pis, Rockboards, and the like are inexpensive by themselves, if somewhat more expensive when adding on things like cases and peripherals. End-of-life Chromebooks might be obtainable for a song and then, with the help of a useful tutorial and a script or two, be transformed into Linux machines (barring physical issues with the components of the Chromebook.) As a general rule, I much prefer giving a learner a machine they have full access to so they can tinker around and learn to their heart's content, rather than being directed into one or another acceptable app pathway or similar.
SBCs or repurposed Chromebooks could put a computer that's okay to mess around with and okay to break in the hands of someone who really could use a non-essential computer to do all of that learning, coding, practicing, and breaking and fixing with. Someone with more technical expertise has to provide the beginning impetus, and possibly help someone through the appropriate steps to get started, before making it possible for them to go off to the races on their own learning. And the machines themsleves have to be available dirt cheap for widespread adoption, or they have to be bought with the intention of giving them away to those who need them. (Which itself might mean there has to be some additional modifications to a stock installation that makes it even easier to use.) Still, I think there's a lot of potential in the space of providing and working with inexpensive low-power devices like SBCs for STEAM learning as well as putting an actual computer-computer in the hands of someone who could use one to play around with. So if you have the budget and have to choose between various options, choose the one that lets your participants have full access over something that's limited and more "toy-like," because while the greater potential space is intimidating, it ultimately allows for a greater amount of learning and self-directed learning, which is what Maker Mentality tries to encourage.
And, of course, there are the simple tools that can be used to create complex structures and machines. Bricks, blocks, planks, straws and connectors, megnetic tiles, and construction kits are high on the "unbounded creativity" scale and really good for programs where there's a suggested goal and no hints on how someone might achieve it. This goes in the big budget section because while individual kits might not be expensive, it becomes clear quickly that having a surplus of possible supplies is the best way to engage groups of participants, and so you start looking at the costs for hundreds or thousands of the individual peices, and that gets very, very expensive quickly, unless you luck into having people near you who have already done the work of collecting large amounts of those materials and they're willing to donate them or sell them to you for a nominal fee. Buying big gives you the best deal, even as it eats a signficant part of your supplies or programming budget to get those tools into your program spaces.
That said, once you have them, and enough of them, you can pretty well do anything that they'll let you do with them. Stack them high, try to follow blueprints or challenge cards, see if you can build something that fits an ecological niche, build a functioning machine to achieve a desired goal, or that can go so far or so fast or any other situation. Or leave them out and see what your participants will do when left to their own imaginations and the ability to grab as much material as they need to bring that vision into existence.
What really works well with this is the truth that when all you have to potentially solve a problem or achieve a goal is a pile of similar-looking resources, there's no secret knowledge that the facilitator has that the participants don't. So everyone is learning, is experiencing frustration and building resilience together. It's also pretty good for a situation where the participants will get to see the facilitator try ideas, or suggest ideas, and see if they work or don't, or whether they're accepted or not. Having a big pile of building materials is really good for shedding preconceptions. But they can be both expensive and take up an awful lot of space when you finally have enough of them to use.
These are a tiny sampling of possible programs, but hopefully this is enough to give people the opportunity to play and to develop their own ideas based on what's available to them.