ADDS and AOPA are good. I tend to go to DUATS just because I'm used to it, and I try to have the radar display in front of me when I call FSS. I still much prefer calling them if it's possible -- I want a live briefing with a real person, especially because it's still possible to get a local who knows the area well, and gives me better information as to trends, etc.
Besides, that way I get statements like "WHOA!!!! No, no, no!! You don't want to go THERE.... it's UGLEEEEEEEEEEE over there!!"
That's one of my favorite briefings.. I responded, "HOW ugly?" And he said, "Ooooh, uh-uh-uh-uh-uh-gleeeeeee!" It was so funny.