KathrynH - Thanks for the sympathy. Actually, you just reminded me that I meant to take him to a busy park and ask him to just sit and observe how kids play together. Honestly though, he generally has a hard time sitting still and watching (which is part of the problem!!!) His little body just wants to be moving.
indigo - I have been trying to set up more one-on-one playdates recently, with mixed results. It seems that if the kid is someone he's known for a long time, the playdate goes fine, but if it's someone a little less familiar, as soon as the other kid starts to draw away, DS just gets louder and more energetic. Sometimes I've tried to step in and talk to him about being "overwhelming", but generally by that time the damage is done. Maybe I'm just not a good coach - after all, I don't feel comfortable in a lot of social situations, either.
Do social skills classes help with overeagerness? Or are they more geared toward kids that are more shy or bad with reading other kid's signals? DS appears to be able to read signals, but just doesn't react in a way that will get him what he wants. He's such a genuinely nice and friendly kid, it breaks my heart to see him get rejected over and over again.