One of our local tech mentors here in Des Moines released a free Excel file for these sorts of projections (an accompanying book to explain the models, etc is also available from Amazon).

You can download here: http://www.startupmodels.com/download/

I haven't used it myself but I know that it has helped quite a few companies work through their financial projections around here. It's at least a decent starting point.

(More info: http://www.siliconprairienews.com/2011/10/startup-models-see... )