If you've tried everything else, I suggest you try CoolBook. It lets you undervolt your processor, which greatly helps with the heat since (apparently) it's the voltage that determines how hot your processor gets, not the clock speed. It costs $10, but in my opinion it's well worth it. My T61 runs cooler in OS X than Windows.

If you don't want to pay, you could try to undervolt using VoodooPower because I think it can do it now, although I was never able to figure it out. In CoolBook it is extremely straightforward.