You can download the Service Pack 2 CTP from the following URL:
The build # is 10.50.3720. This service pack contains all of the fixes from Service Pack 1 & Cumulative Updates 1 through 5, and a couple of other minor fixes (a couple of SSRS bugs and a bug about an ALTER TABLE batch not being cached correctly). It does not include fixes from Service Pack 1 Cumulative Update #6, which I mentioned recently.
You should *NOT* install this service pack preview if: