If you frequently send invoices to your clients, doing this by hand or filling out a template each time is not an option, especially if you bill by the hour and like to give your clients a time sheet for what they are charged.
I have been using the cloud-based billing solution Freshbooks to handle my time sheet, expenses, invoices, and payments for some time now, and do not see myself switching any time soon.
Freshbooks includes a web-based timer which can be used to log time. Their service includes time log overviews, expense tracking, and payment tracking, all integrated with invoices. It even provides a way for your clients to pay online.
They have nicely integrated all of these components with each other while still providing enough flexibility for my needs. It has been a great time-saver, especially since they also generate reports and summaries that I have found very useful.
How do you manage your invoices and billing?