Sysinternals offers several free tools we use like Process Explorer and Autoruns. Also, Mark Russinovich who found that Sony was using a rootkit for some of their music CD's is one of the founders of Sysinternals.
Right now, Sysinternals is still available, but it is running a bit slow. This story has been posted on Slashdot, so that may be why. Another site, Wininternals, which offers enterprise solutions, has already been changed to reflect Microsoft buying it.