alcohol works but it doesn't really dissolve the TIM.
If found this works good. Yes a ripoff @ $7 for small bottle (good for 10 GPU at least) but it works very well.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835100010For cleaning up bad thermal paste jobs which got some of the resistors I have found a method which works well. Using the #1 cleaner in the link above, let it dissolve some of the thermal paste, mop it up with qtips. You aren't really scrubbing it (which just smears the paste around to other resistors) more using the qtip like a sponge. It will take 3 or 4 passes but you can get any surface perfectly clean.
I just watched the video on the newegg link above and was surprised at the "grain of rice" application of the thermal paste. I've been reading that "less is more" when applying this stuff in other posts here, but had not seen how little the "less" reference is. I'm assuming that a GPU application is the same as the CPU application in the video above? I've got a 5970 that is requiring close to 100% fan to keep at 72C and think I will see what this could do to drop the temps/fans to be more in line with the other two cards that I have.