Please remember that StokeIt is free for personal use. If you are a home user, you don't have to pay for it. Really, it's free, you can take it and not look back. That being said, if you really want to make a contribution, I wouldn't dream of arguing with you.
One of the best donations is time and effort. The documentation is seriously in need of attention so if you've got some writing skills, it would be a great place to donate your time and abilities.
If you're a developer, why not take a shot at making a plugin. If you know some C, you should be able to jump right in. If you run into trouble, post a message in the forum and I'll be happy to help you out.
Speaking of the forum, we can always use some more friendly, helpful volunteers to forums and help answer questions or toss out improvement suggestions. Why not volunteer some of your time to answer questions and join in the discussions?
Of course, if you're really looking to give something more tangible, perhaps you'd like to donate something other than cash (books, computer accessories, something from my Amazon WishList, or anything else you'd like to share).
If you're set on contributing money, you can donate any amount directly through this PayPal link. If you're not into the whole PayPal thing, you can contribute in $10 increments by simply buying licenses with the "Buy Now" button at the side of this page. Be sure to send me an email if you do, just so I can thank you personally.
I can't say it enough, but your donations really are very apprecaiated. Thank you.
-- Jeff Doozan