Man, I know I'm going to leave a bunch of folks out.
INTPs: My INTP Wimmenz group always thinks and acts very much like I would IRL, and I love interacting with them. INTPs that I most often get that "YES, exactly!" feeling with--Jennifer, kelric, jockthemotie, Aderack, Martoon, ajblaise.
Non INTP folks that I feel are pretty braintwinny with me: EffEmDoubleYou, jenocyde, Kangirl, Udog.
There are also a good-sized group of people that I relate to otherwise, though, in a complementary way. I feel like Pink is a big complementary person for me--she comes from a different starting place than I would, but I totally get it, and then marvel at the way her brain works. <3 I'm not going to list everyone that I relate to in an "I think you're cool" way, because we'd be here all day long, and I would definitely leave someone out unintentionally. Gah, it's so tempting, though.