We've just built a Time Tracking app that integrates with Xero (online small biz accounting) called MinuteDock.
http://minutedock.com
It was built nights+weekends, around "pay-the-bills" work and a never-ending stream of other projects ;)
Basically, we decided to build MinuteDock as an exclusive add-on for Xero (using their API - http://blog.xero.com/developer). They've been really good to us - offered a possible blog post and a spot in their newsletter.
Before we get sent out to ~12,000 Xero customers though, we'd really like to make sure we've got the product somewhat right. I usually enjoy the Review my Startup posts on HN, and this seemed like the perfect time to give it a go for myself.
US-based HNers: Do many people use Xero for their startup's accounts? Have you guys even heard of it?