Online Customer/Project/Billing Software

I'm looking for a web based tool to manage my customers and projects. I'd like to be able to enter new customers and jobs and generate invoices online. I've tried a few open source offerings (phpaga, jobtracker, etc.) but they all need a bit of tweaking to fit my needs. Since they're open source, I could modify them. But I'd rather use something that worked out of the box.

Has anyone used a product like the one I desciribed?

Thanks for your help.

Jacob Behm