The most popular one is probably the free download from RealTraps. It only goes up to 300 Hz but most of the exciting room response issues happen below 300 Hz anyways.

I purchased a nice test CD from Rives... one of my friends borrowed it... so I'm using the download from RealTraps ;(

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8