Algorithms

Good Web Sites to train your algorithmic skills:
http://www.leetcode.com/
http://www.careercup.com
http://www.topcoder.com
http://codeforces.com
http://www.spoj.com
http://uva.onlinejudge.org
http://projecteuler.net
http://www.usaco.org
http://prepare.hackerearth.com

Site for collaborative coding: http://collabedit.com
Source Code of the most popular data structures and algorithms in JAVA http://code.google.com/p/java-algorithms-implementation/

All the algorithms are implementations of algorithms described in Introduction to Algorithms book A web page useful for online interviews: http://collabedit.com It allows two or more people to work on one code together, by just knowing the exact address.