neo.tax - automated R&D tax credits for startups = extra month of burn
Startup Return Calculator - How much money can your startup investment make you?
Stripe Atlas Taxes - Help file your business taxes
Harpoon Revenue Goal Calculator - Freelancers, how much money do you need to make?
Quarterly Tax Calculator for Freelancers - See how much you owe to state and federal in 7 sec
KnightOS - An open-source OS for calculators