Nobody stepped up to the plate to take on Dave's Soul Calibur challenge, so I did it. :-) To be honest, I was looking for an excuse to hook the Dreamcast up to my capture rig and give it a run.
I'll expand the FAQ on how to take screenshots of console games in the near future, but for now, remember these easy tips:
Don't go overboard on a capture card: Any cheap card (or videocard with built-in capture) that can capture 640x480 at as little as 10 frames per second (30 is best) to a hard drive is more than acceptable for capturing still shots.
Capture an entire session, then go through it later for the frame(s) you want. Don't try to capture individual frames while you're playing -- this seriously affects gameplay ;-)
If there's a lot of motion in the scene and you see "tearing" or "comb" effects due to the interlacing, use a paint program like Adobe Photoshop or JASC Paint Shop Pro to deinterliace the frame. (Pick either one field or the other, but don't blend them both together or you might end up with a blurry mess)
If an emulator exists for the console platform that works very well (ie Bleem for the Playstation), it is acceptable -- and easier -- to use that instead of trying to capture them yourself.
For an example of (what I'm pretty sure is) emulator screenshots, check out Soul Blade. For live captured shots from a real Dreamcast, see the aforementioned Soul Calibur entry.