Place a paypal donate button on your website, like this one:

If you like this website donate me 1 Euro!How It Works
PayPal Donations is easy to set-up and use:
1. Log in to your
PayPal account
2. Click on the Merchant Tools tab
3. Click on the Donations link
4. Specify the name, amount (optional; if you leave amount blank, your donor will be asked to choose a donation amount), and other details of the donation
5. Add more optional information such as a customized button graphic and the ability to include a note with the donation
6. Click Create Button Now and the Button Factory will generate customized HTML code
7. Paste the HTML code on your website to create your Donate button
When a buyer clicks the Donate button, he will be taken to a secure PayPal payment page, where he can log in to an existing PayPal account or sign up for a new one, and quickly complete the transaction.
IF you are using an ASP.NET site put "validateRequest=false" in the page directive IF you are using encrypted e-mail adress in the code of the button (!)