I have a first-generation Macbook Pro (2006) and it has always run pretty hot. The underside gets pretty warm and the thin strip of casing between the keys and the display could cook a strip of bacon.
This hasn't been a huge inconvenience for me until recently, when I had to start running Second Life on my laptop for a work project. The problem with SL is that it is extremely graphics intensive, so the laptop reaches temperatures comparable to a solar flare. One of my friends told me about smcfancontrol, an application for the Mac that lets you control its fan speed. So, you can actually increase the fan speed to cool your computer faster, if need be.
Now, I am not usually a fan of overriding hardware controls, but in this case there definitely seems to be something wrong with how the fans are tuned. I usually only override fan speed when I'm running SL and the temp gets up around 70C.
One of the cooler things, I think, about SMC is that it displays the current internal temperature of your Mac, along with the current fan speed, in the menu bar. So, you can actually see what's going on inside your Mac.
Anyway, if you have a Mac that tends to run hot, this app might be of use. However, I make no claims of knowing the effect of using such a tool on your warranty. :)