My partner and I just finished hashing out the basic design of our conflict resolution mechanic for our system, and we've reached a compromise we're both happy with.  There's a slight problem that's holding me, and thus technically both of us up -- neither of us are particularly good at math, specifically probability.  We're trying to suss out how the percentages with our dice system will go, but are having difficulties calculating probabilities.  Does anyone know a place where we can get this calculated quickly, without having to do thousands of rolls for testing?

Here's a couple of dice rollers that give some very basic statistics (I haven't messed with them much, so you'll have to play around with them):
http://topps.diku.dk/torbenm/troll.msp
http://anydice.com/

What's your dice mechanic, and what kind of statistics are you looking for?  maybe I can spit you out a formula and some basic stats/probs or something.