I have posted this short tutorial on how to add a Paypal Donate button for some of you who haven't known this stuff yet. The process is very simple, just follow the tutorial. I hope this will help.
1. Login to your Paypal account.
2. Go to 'Merchant Tab'
3. Scroll down the window and click on the option "Donations" in the right sidebar.
4. Click 'Create Button Now'
5. Copy the codes. Go to your Blogger, add an HTML/Java widget and paste the codes. Click 'Save' and 'View Blog'
There you have it, your Paypal Donate Button.