We have visual search thanks to Neven Vision and long overdue launch of Googles, and we even have music now, but still no QbH!

http://en.wikipedia.org/wiki/Query_by_humming
Blog(oscop)ed in 2003, http://blogoscoped.com/archive/2003_08_03_index.html

Wished for in 2007:
http://blogoscoped.com/archive/2007-03-21-n83.html

Examples include:
http://www.musipedia.org/
http://testbot.cs.northwestern.edu/beta/
http://blogoscoped.com/archive/2007-01-27-n49.html