We had R2LA IV this weekend at my place. Loads of R2's and other droids! My R2 pictured with the R5 is the only fan made, main character LFL has used on screen (TV) acting as the character (so far...at least it's a first. I'm sure there will be some 3P0's doing this soon.). There were about 50 people (about 25 builders plus family and friends), went from 11am till 1am.
Go here to see 12 Interactive R2's doing a synchronized cantina dance.