Did you know that a laptop can double as a vacuum cleaner? At least that's what it feels like when you go in to clean out the heatsinks around the fan(s), and find what seems like a vaccuum cleaner bag's worth of junk stuffed in there! Especially if you take your machine just about everywhere, the dust stacks up. Mine is nearly constantly on, frequently doing video compression, which spins the fan a bit faster to keep the chip cool. With all the hours of uptime, a bunch of furry lint collects on the heat sink.
Every six months or so I open the system up to clean it out, and this morning it was again due for a cleaning. Here's a video showing the approach:
Video: Cleaning lint out of a Dell D600 (5:35, 18 meg WMV)
The model is an older Dell D600, and virtually every modern laptop in a dusty environment will collect a wad of fur in the same way. If you've never cleaned your laptop then you're probably in for quite a surprise as to how much is stuffed up in there.
Once cleaned you will probably notice the fan running less often or at slower speeds, and better airflow coming out of the exhaust area. Also slightly longer battery life not having as much power drain to keep cool.
Disclaimer: Of course this kind of approach could void some warranties, and carries with it the inherent risk of damaging the machine. I assume no responsibility for the ultimate outcome if you decide to clean your own laptop. I present this instructional video only as what I think is a good idea, geared for those daring souls that are comfortable in taking the risk of opening their laptop. You would want to back up valuable data on the system before embarking on this procedure, and certainly you would want to make sure the unit is turned off first (!)