I came across a site www.donationbooster.com It uses paypal. Allows you to email those people that donate, and if you want, display the top 5 people who donated.
There are two versions. The free version contains and extra link to some other website (its at the bottom of the graphic). The paid version ($4.99 a month) has no additional links. Both version display a graphic that shows your progress towards your goal. For more information go to www.donationbooster.com
When I pasted the code into a blog, it whacked my formatting....
Links