If you've got Rock Band 2, go get it and put it in your Wii! Or, rather, load up some Wii Points and then do that! A bunch of Rock Band forumites discovered that DLC is available today, and Harmonix has just made the announcement!
As of now, Harmonix says that 50 songs are available on the store, including the 20 promised free tracks -- although one user reports a list of 62 songs. According to the announcement, "In the coming weeks and months we will be adding more songs from the back catalog to catch Wii users up with other systems". The tracks that aren't free cost 200 points each. Check after the break for the official list of 50 available tracks. Or just go download stuff. But be warned, you'll probably face some annoying errors and disconnections -- and even freezing systems, according to the forum -- due to the rush of downloaders.