Allot of people change their gtk themes, icon themes and background but not that many people change their system fonts.
Neither did I, untill I read a post on a forum suggesting to do so.
It makes a difference, a big one!
(click on the pictures to view them full-size)
The default font
In ubuntu, you can add fonts by opening a terminal (applications -> accessories) and typing
Then navigate to “fonts:///” and add your fonts there. (press the button under the back button to be able to type text).
You can find allot of fonts on http://www.dafont.com.
There are some Microsoft fonts in the ‘ubuntu-restricted-extra’ package.
To change the fonts on your ubuntu PC, navigate to “system -> preferences -> appearences” and press the “fonts” tab. From there on out you should be able to figure things out yourself.
note: the font on the second screen shot is called “comic sans ms”