UPDATE: While FreshBooks is still a viable solution, I have now switched to RoninApp.
For service oriented businesses, you may be interested in finding a web-based billing software. Of course, we always recommend using the Web Invoice plugin for WordPress, but this may not be enough to meet your needs.
So if you want a more fully featured billing solution that also offers project management, time tracking, and online billing, we highly recommend Freshbooks. Freshbooks billing, invoicing, and time tracking solution, as an online service, is by far the best available on the web. We’ve tried many different platforms and software, but Freshbooks takes the cake.
You can sign up for a free account by clicking any of the Freshbooks links on this page. With a free account, you can manage up to 3 clients. If you like the solution, add up to 25 clients by upgrading to their lowest billing solution, which is only $14/mo. They will even customize a package that’s just for you.
Have you tried Time59 (www.time59.com). It features time and expense tracking, online invoicing, and accounts receivable. $49.95 per year for unlimited use.
Yes, I’ve seen time59. It seems very functional and the pricing is reasonable. However, it appears to lack a demo to try it out and several features that Freshbooks has implemented, such as client login, for example.