A way to track bills and who owes what

What: BillMonk, based on Capitol Hill

Who: Gaurav Oberoi, co-founder with Chuck Groom

What it does: A free site for people to track money they owe (or are owed) and to keep a record of who borrowed their stuff.

Employees: Two

How it works: The site offers to help friends and roommates work out expenses. If one person pays the rent, for example, and the other person pays the utility and phone bills, BillMonk takes the information and figures out who owes whom money.

Amazon.com ties: Oberoi and Groom met at Amazon.com. Oberoi was a developer on browsing services that categorize items on the site, and Groom designed metadata services for cataloging. Both left Amazon last year.

Inspired by a trip: Oberoi said he got the idea for BillMonk after a trip with three friends to Paris and Amsterdam. Before they left, the group agreed not to quibble over who paid for what. They logged it into a journal and worked it out when they returned. The BillMonk site went live in January.

A young audience: BillMonk's target audience is college students and young working professionals, Oberoi said. "Basically anybody who finds themselves in situations where they're in groups and they're sharing money and things," he said. Now, three-quarters of the site's 5,500 users are between 18 and 27.

New features: That crowd also borrows books, CDs and other items from each other. BillMonk added a tracking tool so people can remember who borrowed what. The user can also keep an online catalog of the items they own.

Clearing it up: Small things can get people upset in bill-paying situations, Oberoi said. "Often it doesn't have to do with the money, but feeling like you're being taken for granted," he said. "With BillMonk it's just clear. People know."

— Kim Peterson