Lacuna Regular

http://www.glashaus-design.com/

MiloTF-Text

http://www.fontshop.com/features/free.cfm

Lexia Readable

http://www.k-type.com/

Fontin-Regular

http://www.josbuivenga.demon.nl/

Devroye

http://apostrophiclab.pedroreina.net/

Reference

hail2u.net - Weblog - よく使うライセンス・フリーのフォント
http://hail2u.net/blog/webdesign/lovely-license-free-fonts.html