If you have been using Linux, I think you must have been frusturated with the lack of good fonts when using Emacs. It gets very hard to distinguish between "l" (the letter l) and 1 (number 1) and between comma and semicolon when programming or examining large amount of code.
The Bitstream Inc have done an excellent work in producing and relesaing under a very liberal license, the bitstream-vera fonts. These fonts are really beautiful and easy to read. To use these fonts with your emacs, just add this line to your ~/.Xdefaults file
Emacs*font: -bitstream-bitstream vera sans mono-medium-r-*--*-100-*--*--*-
Of course, you need to have the bitstream-vera fonts installed on your Linux box