MS only sells licenses for SQL 2012 now.
I'm not sure of your situation, but if your company purchases licenses in bulk, i.e. through a Volume License Reseller, I think you could still download 2008 through that channel.
If you or your company has a TechNet subscription, I believe SQL 2008 can be downloaded there as well. Or perhaps someone in your company has a MSDN subscription, which should have SQL 2008 included.