Maki Map Symbols
The AIGA symbols are good, but as a self-professed map-geek, I'm always on the look out for new map symbols that in some cases may work better across cultures. I recently came upon a growing collection of symbols named Maki that show promise. They're cleanly designed and most of them work pretty well. Here's an interview with one of the Maki designers to learn more about how they were developed.
If the Maki and AIGA symbols don't meet your needs, then head over to the excellent Noun Project site for even more free, downloadable symbols. And remember, if you're going to make a map that uses symbols, be nice to your users and include a key; that's map-speak for a list of the symbols with brief text descriptions next to them.