Microsoft Font Maker - Use your pen to create a custom font based on the nuances of your own handwriting.
Scanahand - Scanahand makes it easy to create Windows Truetype fonts from your handwriting.
YourFonts.com - YourFonts is an online font generator that turns your handwriting into a font that you can use in every program that you own. 500,000+ fonts already made!
My Script Font - Make a font with your own handwriting
FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
Fony - Fony is an editor for bitmap (raster) fonts.