E-flight calculator, free software, source available (GNU license):
WebOCalc - Free, easy power system help! - RC Groups
More e-flight calculators, most of them freeware:
Power Systems - RC Groups
-> e-flight calculators (compilation)
Vriendelijke groeten 
Ron van Sommeren
brushless motor building tips & tricks
diy brushless motor discussion group
Drive Calculator download & discussion group
int. electric fly-in, Nijmegen, the Netherlands