There is a new version of SplitBill out on the market.
Still it allows you to split bills amoung your friends or whatever, but now it also suggests an optimised transaction scheme. This way the number of transactions needed to even out the expences is reduced to a minimum (one per person in the best case).
The only drawback of this optimisation is the fact that larger amounts have to be transfered by each individual. Of course you still get the traditional calculation, so you can choose for yourself.