Do not set your laptop onto a solid anything that does not act as a heatsink. e.g., a solid wood desktop is a bad place to set a laptop. Even if the fans are not obstructed, the wood acts as an insulator to keep heat inside your laptop. On the other hand, if your desktop happens to be made out of solid steel, that would act as a great heatsink, not an insulator like wood.

Get four plastic bottle caps (all the same size) off of soda pop bottles, water bottles, etc. And use those as little feet under your laptop to raise it up a bit off the desk. Even raising it only 1/2" with bottle caps does wonders. It will cool that puppy right down. Throw a few spare bottle caps in your laptop bag so you have them when you are mobile.

[edit]You can buy "laptop chillers". They have fans in them and you set your laptop on top. Problem is, even though they add additional fans, the top of the chiller pad is so close to the bottom of your laptop that it pretty much defeats the purpose. Bottle caps - with no additional chiller fans - work much better in my experience (and they're cheaper too!)[/edit]