[pacaro]

This is covered very well (a long with many other neat algorithms) in The Computational Beauty of Nature[1], one of those books I keep coming back to

[1] http://mitpress.mit.edu/books/FLAOH/cbnhtml/

[elemeno]

A fantastic and seemingly little known book.

Not necessarily for anyone who's not comfortable with the math, but a very rewarding a mind opening read.

[haraball]

The book Clever Algorithms (free to download) is also covering some swarm algorithms: http://www.cleveralgorithms.com/nature-inspired/swarm.html

[raverbashing]

This is a really great book! And a real mind opener.

Even if you know about some areas already.