On Feb 22, 2012, Microsoft released SQL Server 2008 R2 SP1 Cumulative Update 5, which is Build 10.50.2806. This CU has 16 fixes listed.
If you are still on the SQL Server 2008 R2 RTM code branch, you would want to take a look at SQL Server 2008 R2 Cumulative Update 12, which is Build 10.50.1810. This CU only has three fixes listed. Really, I think you should be making plans to get off of the RTM branch, and get on to the SP1 branch for SQL Server 2008 R2, especially since a number of useful new DMVs were added to SP1. Another reason to get on SP1 is that Microsoft will eventually retire the RTM branch, leaving you on an “unsupported service pack” when that happens.
As always, keep in mind that these Cumulative Updates are only for SQL Server 2008 R2, not for SQL Server 2008.