Check out this blog by Dare (I don't work at Dare btw!)
http://trendplanner.com/2008/11/14/this-is-an-ad/
It's called 'This is an ad' and should give you some great examples of a few stunts and exactly who they were actually an ad for.
For Big time check out some of the viral campaign for the Dark Knight, for small time; at my agency we once got sent a blood stained cricket bat with a CV on from a freelancer, taking inspiration from the then recent Shaun of the Dead, suffice to say he got some work.
Good Luck!
Matt (www.trendplanner.com)