How to represent chess state with a bitboard I'm interested in programming a chess engine and using bitboards to represent the state of the game. I know there are a few open source chess engines that use bitboards, but its not so easy to look at the code and understand what is going on. I'm looking for good reference material on how to represent all the state in bitboards.

Clearly explaining how to maintain the state of the game using bitboards, and especially how to generate a list of valid moves from any given bitboard, or supplying good references to such an explanation will earn you the green check mark.
The best resource for chess engine programming is the Chess Programming Wiki, which has a large section on bitboards. Everything you need to make a bitboard-based engine is there, although it's rather spread out and sometimes written by people for whom English is a second language.