Today Microsoft has released Service Pack 2 for SQL Server 2008 R2.
The build number is 10.50.4000.0 and it includes fixes from 2008 R2 SP1 Cumulative Updates 1, 2, 3, 4 and 5. The fixes from Cumulative Updates 6 and 7 will be published in a subsequent cumulative update, so if you're relying on those fixes, do *not* install the service pack until SP2 CU#1 is available.
The SQL Server team talks about it a bit on their blog, but their download link currently points to the 2008 SP2 download. Which will only further the confusion that 2008 and 2008 R2 are the same!
The KB is here but it is currently broken (should be published soon):