Avista

We rented audio equipment for our wedding from Avista. They were very responsive in terms of answering our questions on what kind of equipment was needed for an event our size.

We ended up renting two speakers with stands, a mixer, wireless mic, and mic stand for around $230 total (I think -- it's been a while and I don't have my receipts handy; payment is 50% upon reservation and 50% upon pickup). The equipment was in great condition and worked well. It's tested before you get there, and tested again when you pick up. The technician will run through the setup with you and answer any questions -- everyone we dealt with there was very nice and very helpful.

They have two service locations, one in SF and one in Sunnyvale (which is kind of hard to find -- read the directions on their website before trying to find it yourself or with an online map!). I believe they also deliver/setup/takedown for an extra fee, but I'm not sure on this. They're closed on Sundays, so if you pick up on Friday for a Saturday event, you return the equipment on Monday. They'll lay it all out clearly for you.

All in all, a great experience. They have a lot more A/V equipment than just audio setups. If you're ok with DIY'ing the entertainment portion of your wedding, Avista would be a great choice.