I'm using a 2.6.37 SavageZen 0.0.9-BFS-HAVS-WiMAX-GB+ on CM7 it goes to 1190400, some go higher.
However, I've installed some kernels that went higher, I set it higher and checked "Set on Boot" and ended up in a loop where once Set CPU loaded it couldn't handle it and rebooted over and over.... until finally I was fast enough to open Set CPU before it set the CPU so high, and move the CPU lower. Sooo... careful.
I would search CM's website forum and xda to see what people are using. They recommend a bunch, don't remember how I landed on this SavageZen one but someone convinced me and I've been very happy with it.
Happy Flashing.