[ownproj] Indicates that you can work on your own projects there.
[ownproj] Indicates that you CAN'T work on your own projects there. By working with them, the main thing you gain is skills, not necessarily your own project being completed. (you will, however, complete some of THEIR projects, and you may very well find those valuable enough to want to take home with you)
[$$] Indicates it costs money to work there and use their equipment. (most of the other places are completely free, to encourage community participation) The upside, however, is that these groups pool their money together, so they have may more expensive equipment than would otherwise be available in a community space.