James Brown is my first pick for any party where people will want to talk to one another, along with a few funk albums (eg. by The Meters) and compilations. I realised a while back that it was the perfect party music for me: upbeat, groovy, simple and familiar, and totally unobtrusive (if you keep it at a sane volume). Sometimes I'll throw in some old reggae and even Jack Johnson, however. Oh, and of course Earth, Wind and Fire. Very rarely some MJ from the good old days (come on, how many people are there that don't dig Billie Jean?)
For a slightly more bouncy party, I go for simple and familiar and cheerful rock/pop, pref. classics that everyone recognises, fun disco, some old-school reggae, a ton of mashups (eg. DJ Cheezi's "Mysterious Tweet"
) and my favourite Swedish hiphop, most notably by Timbuktu and Snook (great music, fun, original and familiar lyrics, tunes which very few people dislike, here).
There was a time when I always made sure to play "If I Ever Feel Better" by Phoenix, no matter who was there. But that time is past.
