So, these are some ideas that I've been thinking about for a couple of years now, and I haven't had the time to get them started. That said, I am posting them here in the even that anyone reads this and could take these ideas and use them. I don't need credit for them, you just need to promise that you'll let me know how their working.
1) Guerrilla Art Fair
This one needs some buy-in from your local government if you hope to do it for longer than 3 hours. Or...maybe you don't care.
Call together artists, musicians, spoken-word poets--whatever. Confirm the people that you have and tell them to bring some of their work to a certain location on a certain day. (PLEASE UNDERSTAND: This is NOT a flash mob.)
Make fliers with the names of artists, include what will be at the fair. Pass them out in clubs, bars, tattoo parlors, up-scale coffee shops, etc. It's important that you have a mix of places canvassed.
Have the fair. Ask a couple of artists to offer workshops. Depending on how adventurous you feel, allow people to sell their stuff.
Also very important: Allow places for people to drop business cards, sign e-mail lists. Keep them in the loop for future events.
Evil Plot Twist: Contact any businesses who left information. See if you could round them up to sponsor a proper art show featuring the artists at the guerrilla show.