Here are a couple of quick things you can do to speed up your Linux system. First, add "noatime" to your fstab file by typing sudo nano /etc/fstab and in your root directory line (and home directory if you have them separate), under options add the noatime option with a comma like this (from my Debian fstab file):
And no spaces between the commas. This will greatly reduce the writes to your hard drive as your system will no longer write file access times to disk (not needed for the typical user).
Another quick change is to switch your display's color depth from 24 to 16 (millions of colors to thousands). To my eyes I could never tell the difference on a laptop, so I just opened my /etc/X11/xorg.conf file as root and under Section "Screen" I added a tab space followed by DefaultDepth 16 or if you already have a line for it, just change the 24 to 16.
Using glxgears, the frames per second on my Mom's iBook went from 340 to 550 after the change. Not bad for a few seconds work (and a few hours research).