I upgraded my Dell 700m laptop from Ubuntu Feisty to Ubuntu Gutsy. Gutsy is the current developemnt (beta) release of Ubuntu Linux and is planned to be released in October of 2007. After upgrading to Gutsy and restarting my laptop many of the fonts were too big.
To correct this you may need to set the DPI to 96. To see why read this:
Note: Your fonts may be different than what I have set.
You may need to logout and back in again for fonts to change for all of your running applications.
Also, if you don’t have a LCD display you will not want to have “Subpixel (LCDs)” enabled like I do.
If you want to change what fonts you use read this for tips for which fonts are better for legibility: