Well, I finally broke down and bought an external flash, the Metz 48 AF-1. After missing lots of shots at a friend's wedding reception and then getting roped into acting as "official" photographer for some other friends' annual "flip-flop formal," I decided it was time.
Apparently, part of the festivities at the flip-flop formal typically involve a bunch of drunk people posing with various props and having their pictures taken while making wacky faces. To be honest, this wasn't how I wanted to be spending a party, but it turned out to be more fun than I expected.
I definitely learned a lot about flash shooting over the course of the evening, and I definitely still have a long way to go (especially w/r/t reducing shadows).
Here are a few shots, all with the DA 21mm Limited (best option I had to go wide in such a confined space). Unfortunately, the room was very small, and had various distracting objects on the walls, and I haven't mastered the Photoshop clone tool yet. :o
I intentionally post-processed for a sort of "high-key" look with these: