nice. here's a bunch of nsf files (can scrape with wget): http://nsf.joshw.info/
I grab most of my chiptunes from the various subdomains on that joshw site, and play them with Winamp 2.x + a bunch of input plugins under WINE. Audacious is linux native and has support for most chiptune formats built in, but the sound emulation isn't as developed (missing DPCM sound for NES, 32X). I don't have a SID plugin for winamp yet, but audacious is working fine.