GeekBot - Searches over 11,000,000 open source related webpages.
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.
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()).
Nutch - Effort to implement a prototype of an open source web-search engine.