Good multistage rocket equation calculator

Is there a decent multistage rocket equation calculator
on the web? Just looking for a simple one that accepts the
usual inputs: # of stages, mass fraction, specific impulse,
payload, etc, and outputs the resultant delta V.

-- Joe D.

Not sure that's this is what you want, but there's a half-decent GPL'd
javascript 4 degrees of freedom multistage launch simulator/costing
program (originally written by Enrique Perez.):

http://www.wolfkeeper.plus.com/spacecraftcost4.html