My local creative learning space is a nerd bicycle chopper gang called SCUL. It is based out of Somerville, MA, close to MIT.
'Ship' building - fabricating art bikes. Range: putting glow-in-the-dark stickers all over a bike to chopping up normal bikes and making double deckers (H.A.R.V.s - High Altitude Reconnaissance Vehicles).
'Sonic Disruptors' - portable music players. Range: iPod plugged into an off-the-shelf portable speaker running on AAs secured with duct tape, to the completely homemade subwoofer/waterproof system that run on car batteries connected to LED light strips that pulse along with music.
Fabric art - from making our 'Colors' by pushing buttons to make a digital embroiderer go, to a customized 'plasma casing' (inner tubes) utility bag that can deploy the necessary parts quickly to fix a flat.
Bicycle art - from stenciling choppers to the Exploded Bicycle Sculpture (this, represented with an actual bicycle with actual parts: http://sheldonbrown.com/retroraleighs/catalogs/1977-drawings/pages/22-track-bike.html)
(then there are even nerdier projects that I do like keeping the books, which involved building a whole finance structure, our income/expense goals, projections, risk assessment, etc.)
Ship building typically starts with individual interest. Depending on skill sets, members will help each other out. Sonic Disruptors are definitely of individual interest. Personally, I think we're plenty loud without more speakers. One could argue that more SDs we have, the less we have rely on a select few members to be present regularly, which is fair (so, that would be for community interest). Many ideas come from needs, such as the utility bags that I mentioned earlier. We do have a pretty extensive record keeping so there is a good amount of institutional knowledge that gets passed down, so we can say things like "That thing you want to build? We've tried it. Here were the challenges. You up for it? Do you feel lucky?"
Absolutely people help each other learn. Mentors are not officially assigned, we have a 'hosting' system and the quality and quantity of that training varies depending on each host's interest, their level of participation/ability to teach, etc. Besides our founder the Fleet Admiral, leadership roles are not formerly defined. But, the longer someone participates, one sort of figures out who has been around, who does a bunch of work, who pops in only when it's nice out, etc. We do have (guided and unguided) times set aside for projects, so people can connected with mentors (which are just other members).
We're all mostly adults! Relationships range between Civil -> Close Friendships/Romantic Partnerships. As for community guidelines, we do have a list of "Prime Directives" that are heavily based on respect. It only comes up and gets dissected when we have personnel problems, which surprises no one I'm sure.
SCUL operated out of basements/garages for many years, in makeshift bicycle shops. Over the years we have created other project areas like the fabric arts station to support those interests, but we're largely a greasy bicycle shop. When the Artisan's Asylum (http://artisansasylum.com/) was getting off the ground, their founders approached SCUL, recognizing that we had inadvertently created a thriving community of Makers of very different interests. This was a model they wished to emulate and felt that having SCUL be part of the Asylum could be beneficial to both parties. They were right! We have been operating out of the Asylum since. Now, in addition to a bike shop, many SCUL members ('pilots') are also Asylum members and have access to even more shared resources for Making. For example: More pilots have learned to weld, which yielded more builds both because of talent increase and access to welders.
(....and I've certainly created a lot more spreadsheets!)