These other sites relate to all aspects of Axis and Allies, clarifying rules, offering downloads, other odds calculators, and discussions of strategy. There are a lot more out there, but I find these to be the most useful:
AxisandAllies.org- this is my favourite forum for discussing Axis & Allies. Great community.
Game Table Online - online site to play A&A (free vs AI, or one-time-pay-to-activate vs other users). Great community.
TripleA - turn based strategy game for playing online A&A-like style games (free). Great community.