Microsoft Font Maker - Use your pen to create a custom font based on the nuances of your own handwriting.
FontForge - Free (libre) font editor for Windows, Mac OS X and GNU+Linux
Scanahand - Scanahand makes it easy to create Windows Truetype fonts from your handwriting.
BirdFont - Birdfont is a free font editor which lets you create vector graphics and export TTF, OTF, EOT and...
My Script Font - Make a font with your own handwriting
FontStruct - FontStruct. Build, Share, Download Fonts