Each morning I log in to harvest and get an overview of my world:
This lets me see how the invoicing is going, and also the hours for the day/week/month ... which of course serves to remind me that I didn't fill in my timesheet yesterday :) The timesheet itself is great - super-simple, accessible, and even I've managed to keep it up to date. There is a week view which is simply a grid (client names removed and I'd like everyone to admire my new 40-hours-a-week lifestyle):
It shows totals for activity and day, and the grey hours are the ones I've invoiced for - you can invoice and "lock" the hours so it's easy to keep track of which have been invoiced and which haven't.
The invoicing has been a gift as well, rather than messing about with document templates, Harvest does them really nicely and I can see what's outstanding, overdue, paid, etc.
I got started with Harvest because their free option was enough for me to get started - when I began the business I had absolutely no clients and nothing planned so I didn't have any cash to spend, and importantly Harvest allowed unlimited invoices which was ideal for me as I was doing bits and pieces! Within a few months though I upgraded to a better account which only allows a few users (which is fine, there's one of me) but allows me to have more clients/projects and so on. So far, it's been a great tool and I thank the good folk across at Harvest for making it available :)