I faced a similar question myself and decided to try adsense and adpinions, I put up a little line saying basically if this pisses you off let us know. No one really has, but I'm sure some find it bothersome. I am thinking about doing the wordpress thing and not showing ads to logged in users. If you use hard stats(pagviews,uniques, etc) to get advertisers you may not want to use this method.

I think I am going to switch to a donation based way becuase people either really see the value in my site or they don't and just leave anyway.

Great Question, I am interested in seeing what other say as well.