Fewt, the author of Jupiter and member of the Aurora OS (ex Eeebuntu) core team has a really interesting post on his blog about improving your netbook's performance but also increasing the battery life by moving the temp and log files to RAM using tmpfs.
This is achievable by simply editing the fstab file - you'll basically mount 3 folders in your RAM. Of course, since these files will be saved in the RAM, they will be deleted upon restart but usually you don't need these files anyway.
Fewt's post also includes tweaking Firefox to use the RAM tmpfs for the temporarily files which will make Firefox a lot snappier.
Note: this will of course also works for laptops and even desktops (but obviously, you'll only get a performance boost, there's no battery life to improve for a desktop).
Head over to Fewt for the complete how-to.