I don’t have to track my time for billing anymore but when I did having a good time billing program was essential.  Invotrak is a great online program that lets you track your billable time and generate client invoices.  It was covered a while back by our friends at Web Worker Daily and it is available in a free version with tiered paid versions that add additional features.  Today we received word that Invotrak now has a version available for the iPhone to make tracking time and invoices a handheld process and it looks very full-featured.  If you’re already a member of the Invotrak service you should certainly check it out.