Brew simultaneous extract and all-grain batches. People love it. Set up a literature table, put out some ingredient samples and an email sign-up sheet, and get some volunteers to take turns standing there to answer questions. Get some free copies of the introductory Zymurgy issue (or find someone with a lenient place of business where you could print them for free from the online .PDF.)
Another great thing one of our members did was to make up a huge score sheet by blowing up different portions of it and taping them together from behind to make one big-ass score sheet (BASS), then covering it with clear laminating plastic. We bring it to every public event we have...put it on an easel, hang it from a hook or rope, mount it to a board, or just duct-tape it to a pole or canopy awning.
We do this every year at the Maryland Microbrewery Festival, where the organizer asks us to have educational demos and informational talks. We cannot pour our beers except when it's one of our own brewing events at one of our homes.