A few add-on authors have asked about directing contributions for add-ons to the Mozilla Foundation. You definitely can! If you’re an add-on author and interested in directing your contributions to the Mozilla Foundation, it’s simple and easy to do. Just set the PayPal e-mail to accountingATmozilla.org and contributions to your add-on will be directed to the Mozilla Foundation PayPal account.
You can add the following text to your add-on description so that contributors know where their money is going:
“All contributions for this add-on go to the Mozilla Foundation. Mozilla promotes openness, innovation and participation on the Internet. Learn more at www.mozilla.org/foundation.”
If you have any questions about the Foundation or our activities, please contact us at donationsATmozilla.org or ping us in the #foundation IRC channel. Thanks to Nick and Shawn for this idea!

I assume there’s already a bug filed to make this an available option in the UI for the next update of AMO?
Now that’s a great idea.
I really like this option. Unfortunately, the contribution message suggests that the contribution will go to the add-on developer and the add-on description is way below it (easy to miss). This feels like giving people wrong expectations. Is there already a bug to add individual text to the contribution message? At the very least Alexander’s suggestion should be implemented along with a different (not misleading) message for that case. Once that’s available I will happily redirect Adblock Plus contributions to Mozilla Foundation.
Very much agreed. This process could be a lot clearer. I’ll add this suggestion to the bug as well. Thanks!
Bug filed. Please feel free to add your suggestions to it as well! https://bugzilla.mozilla.org/show_bug.cgi?id=545132
[...] through AMO: Suggested Thank You text 16 04 2010 Are you one of the many Add-on authors directing your contributions to Mozilla Foundation? If so, thanks so much! Also, to make setting up your contribution module [...]