I use TVersity, but only for streaming Sirius radio to the 360. I tried to use it for everything else, but I found the UI to be terribly akward.
For music from my own collection, I use Orb. Winamp Remote works too (based on Orb).
For movies, I connect a usb drive containing the movies directly to it. Orb can stream movies too, but I find that it always plays them fine for a few minutes then starts to get out of sync and buffer way too much.