AceInvoice

AceInvoice is a time tracking and invoicing application.
This helps to track time spend on different tasks in a project by using time entries entered by team members. It allows team members to enter time and admin to generate invoices to clients based on that.

It has a powerful invoicing system. It keeps track of various changes in invoices so that you can inspect them. In addition to time entries it allows to include other expenses such as hosting and other services in the invoices.