Many of the events can not afford a photographer, so how do you recoup your costs? Do you put out a tip jar? There is an easier way ... SmugMug.
Check out Vince Gervasi Photography. Vince was a few years behind me in high school. Fast forward to a month ago and Vince was shooting my 20 year reunion. His model is simple, efficient, and brilliant. Put the photos up on his site, which is powered by SmugMug, and let those that are interested in the photos purchase their favourites. You may end up with a larger take from the event (vs. a flat fee) when you spread out the income stream in this way.