Of course, Neocha's NEXT player is always one of the best places to go if you want to hear some underground Chinese music and most of the bands I write about have Neocha or Douban pages (if not both) where you can stream songs and occasionally download some stuff too.
For Sonnet, if you downloaded their EP for free and enjoyed it, you can download their live set from the Michael Jackson tribute night here. It's shared via RayFile which a lot of the bands seem to use at the minute. You have to download some software first (doesn't seem to work on Macs, sigh) but it seems safe. You can get the Billie Jean and Smooth Criminal covers as tracks on their own from Sonnet's Douban artist page too.
I mentioned a little while back about Five Pointed Star bringing out an EP soon called Awake. The release party isn't until the 29th, but you can have a little preview listen here. All clips rather than full tracks and only available to stream, not download I'm afraid, but isn't that what the kids are into these days anyway?
Another link that might have got buried at the bottom of an old post, is this one here to a live recording of Zhang Weiwei and Guo Long of Glamorous Pharmacy. If you like your folk/acoustic stuff, then this is definitely worth a click. To hear Glamorous Pharmacy themselves live at YYT, go here and click play on the bottom track to listen to them doing 脚步声阵阵. For more folk/acoustic stuff, check out Fanqie Chaodan's page where he's put up a few new tracks in the last few weeks too.
Finally, a couple of things for you to watch. One is this interview with the Handsome Furs about their recent tour of China where they offer some interesting views on the Chinese music scene and its exposure in the Western press. The other is the band themselves performing at YYT.