Google Code Search

http://www.google.com/codesearch

Koders - Source Code Search Engine

http://www.koders.com/

codefetch

http://www.codefetch.com/

Krugle - Code Search for Developers

http://www.krugle.com/

byteMyCode

http://www.bytemycode.com/

Codase - Source Code Search Engine

http://www.codase.com/

Java Examples - JExamples.com

http://www.jexamples.com/

DocJar: Search Open Source Java API

http://www.docjar.com/

Prospector Demo

http://snobol.cs.berkeley.edu/prospector/

KickJava.com: Java API By Example, From Geeks To Geeks.

http://kickjava.com/

Jarhoo

http://www.jarhoo.com/content.jsp

All The Code - Source Code Search Engine

http://www.allthecode.com/

Code Search - O'Reilly Labs

http://labs.oreilly.com/code/

Reference

@IT - 見つけて得するソースコード専用の検索エンジン
http://www.atmarkit.co.jp/fjava/column/andoh/andoh33.html