If you use PayPal for receiving payments and/or printing postage here's a tip for printing out reports of your transactions. When in your account above your recent activity is a link that says All Account Activity, this gives you lots of great printable reports yo can use for accounting, taxes, etc.

You'll see that you can set date ranges which is pretty straight forward, you could get reports for a specific month or year if you want. What's really great is the drop down menu above the dates, this lets you select only certain transaction to show, payments you sent, payments received, shipping payments, withdrawals, etc.