I shared a Numbers template two years ago that helped me estimate my 2007 taxes. In 2008, I co-founded Calf Trail Software, LLC, and let an accountant do the filing. That luxury ended up being a major financial setback, so the spreadsheet is back:
I’m sharing my efforts under a Creative Commons license again, so you can download my 2009 Federal Tax Form 1040 worksheet as a Numbers.app template.
Reminder: Don’t trust the results of this unofficial spreadsheet. It is not a substitute for the official forms, instructions, tax tables, or the advice of a certified accountant. Please do let me know if you find any errors, though.