Sourcebank:
Full-text search engine for source code.
http://www.sourcebank.com/
GeekBot:
Searches over 11,000,000 open source related webpages.
http://geekbot.org/
KDE CVSSearch:
Allows searching the KDE project CVS repository using CVSSearch, a
new kind of tool for finding code fragments by looking at associated
CVS comments.
http://horn.cse.unsw.edu.au/~cvssearch/Query.cgi
KDE GUISearch:
Allows searching the KDE project CVS repository using GUISearch, a
new kind of tool for finding code by looking at the applications'
GUI text messages (e.g., "Undo") and returning associated
callbacks/slots (e.g., slotUndo()).
http://guisearch.sourceforge.net