I've never had so much trouble getting sound to work in Linux before. I have the correct modules loaded (snd-intel8x0), I can adjust the volume in GNOME, and I have all the levels bumped up in alsamixer. Beep Media Player and GNOME even show my sound chip being Intel ICH6 (Alsa Mixer) Master. For awhile I could play an audio file and see the visualizer bouncing around, but I got no sound at all. Now, I get "Couldn't open audio" in Beep Media Player, followed by a complete freeze of GNOME, and MPlayer locks up when trying to play any file. What the hell am I missing?

hmm... Do you have esd running? That may be taking over /dev/dsp and keeping anything else from taking it back. Try disabling it and starting bmp or mplayer again.