One thing that Splitwise has turned out suprisingly useful for is group trips: road trips, ski-trips, weekend getaways, whatever. It’s a classic money-organization problem. Someone rents a car, someone buys the groceries, someone pays for gas, and lots of money is getting lent back and forth. Without Splitwise, someone always ends up spending a few hours trying to reckon it at the end, and then someone gets confused and you do it over again. And then you have to figure out how to pay each other back, and money just gets lost in the shuffle.
Together, Ryan and I have used the site for 5 trips already. I’m currently staying at a rental house in Michigan with 11 friends in celebration of the wedding of my friends Lauren and Ben. We’re having a blast, and the people staying in the house love how non-stressful it is to just dump everything on the site – groceries, park passes, gas, the house rental, and beer runs. Once one of us enters the expense on the site (say, a grocery run), we just forget about it until the end of the trip. Kara loves how the site reduces the number of payments, so that if Rebecca owes Kara money and Kara owes Eve money, it just keeps track of the balances so that in the end Rebecca owes Eve. At the end, you can also see how much the whole trip cost you individually, which is a bitch to figure out without a computer.
To share a trip on the site:
1. Create an “apartment”
2. Add all your friends to the “apartment”
3. Everyone adds expenses that they pay for
4. Pay each other back at the end
The Splitwise Blog 
Never thought of that! So far i’ve used the iphone app “payback” with great success. I’ll give it a test for the next trip.
Our iPhone and Anroid apps are going out really soon – stay tuned!