@blakespot
dvplayer is commercial, and there's a new version coming, but until then, i'm not sure if you can order it anymore. try
dvplayer.amistore.net and see if it will let you buy it. if not, ping matthew (@amigakit) or trevor (@TrevorD) and see if they can help. the version included as an 'extra' with the OS is really more a demo. but i used the full, paid version on my SAM back in the day, and it played 480p AVIs quite well, especially in fullscreen.
mplayer is another animal altogether. for faster NG machines, you don't really need to fiddle with it, but man, i had to on that SAM. you want to make sure framedrop is always enabled. if it's an AVI, you want cache on, if it's a MP4, you don't and you also want force indexing... see what i mean? eventually i just used my office machine to transcode all my video files into 480p AVIs using Xvid or MPEG2 as a codec, and those work great. i was so happy when i got a G4-based system. it played everything, no need to muck about. and, no, there is no VLC port -- at least that i know about.
as for what else, well, there's a bunch of stuff out there (as i mentioned earlier), and plenty of cool games, too. are there any specific things you want to do with your SAM?
-- eliyahu