I didn't see this posted anywhere on the main page or TAY, but I could have missed it. Anyhow...Blackthorne, Lost Vikings, and Rock n'Roll Racing are free to all Battle.net users.

Details here: http://www.kotaku.com.au/2014/05/grab-t…

Rock n'Roll Racing claims to be a "lite version" with only three tracks...but it is free, so whatcha gonna do.