Microsoft has released cumulative updates for SQL Server 2008 R2.
SQL Server 2008 R2 SP1 Cumulative Update #8
Note that the page that lists builds and updates for SP1 doesn't currently agree with the KB article; the KB article shows 10.50.2821 while the build list correctly shows 10.50.2822. The download is certainly 10.50.2822, so only the KB article is wrong.
SQL Server 2008 R2 SP2 Cumulative Update #2
Similarly, the page that lists builds and updates for SP2 also contradicts the KB article; it currently states that the build is 10.50.4263, not 10.50.4261 as the hotfix KB shows. Again, the file agrees with the build list, not the specific KB for this cumulative update.
Note: Some of the fixes in SP1 CU#8 did not make it into SP2 CU#2. Those fixes will be available in SP2 CU#3.
My usual disclaimer: these updates are NOT for SQL Server 2008. Only apply to systems where @@VERSION returns 10.50.xxxx, where xxxx is >= 2500.