You may never think about the fonts on your computer unless you do a lot of design work or get bored with Times New Roman, but cool fonts can release creativity while working in your favorite graphics application or even typing out a letter.

Dafont, GRSites Fonts, and 007 Fonts are three of the largest Font Sites, has just about every style you could want. Fonts are listed in alphabetical order by font name and lists the license. Most are open or free.

For some of the best designer fonts Fontennium will certainly fit your needs. These are all free. If you're looking for grunge fonts Misprinted has some free fonts listed on their site. 

For the alphabet of the witch grab some Theban fonts. 

These are high quality fonts, which I have used in many projects. I have no problem using most of these fonts in Linux.

 If you're a purest and want to make your own fonts Fontforge is certainly up to the task. I use this on Linux, but there is a Windows and Mac port.

Have fun.