Thus far I’m quite in awe of how many people have offered to contribute towards Flagfox development. Thank you all! 🙂
I’m using Mozilla’s addon contribution system through the Mozilla Add-ons site & the Firefox Add-on Manager (Firefox menu button -> Add-ons -> Flagfox -> more -> scroll down). This is their recommended way to do things and I thought it would be more trusted than just sticking a button of my own on this site. (links are in the sidebar to the right, as well as here)
It has thus far had about a 98.5% success rate. A few people have emailed me to complain that it’s not working for them. Thus far we don’t know why. My general recommendation is to make sure you’re not blocking scripts or cookies needed by PayPal. (neither of us may be thrilled at their implementation, but you might need to unblock something to get it to work) One person said it didn’t work for them on multiple computers with multiple browsers, so it’s possible there are international usage issues as well. Unfortunately, because I am using Mozilla’s system, I don’t have a way to debug this myself.
One person suggested I just tell him my main email address so he can send with PayPal more directly. This seems like a good work-around to me, so if anyone else has an issue getting things to work, please email me using the general feedback email address (also linked to in the side-bar to the right). I will reply with my main email address which is hooked up for PayPal. The email address I use for receiving general feedback is different to make dealing with the spam flood a bit easier, so you can’t use that one to send me donations.
The Amazon route is also available to those who wish to use it. If PayPal doesn’t work or your loathing for PayPal is too high to create an account, you can also contribute with an online Amazon gift card. Very few people have opted for this route, though I just confirmed today that it is working. It has the benefit of not having fees but the disadvantage of locking the donation into Amazon-money. As long as this is not used too much, this is quite fine as I will be purchasing some things I need to develop a mobile version of Flagfox using Amazon.
Edited to add:
Also, please avoid sending only $1 via PayPal. I really do appreciate the thought, but with such a low amount PayPal takes a third of that for its fee. (there is a buried microtransactions fee system, but based on average donation I think the fees are less using the normal fees; not sure yet, though I’m sure I hate the way they manage this) Sorry, this is of the many reasons people aren’t always fond of PayPal. 
Flagfox 
Have you tried v.me by Visa? I signed up but haven’t used it yet.
No I hadn’t heard about it until now. Thanks for the suggestion.
Unfortunately, Mozilla only supports PayPal for their contributions system. They’ve gotten quite a few requests to allow alternate systems, but as of yet this is still the only route they support. (the contribute button on the official page and in the Addon Manager inside Firefox) I might consider using Visa’s system if someone wanted to directly send me a contribution and was not capable of using PayPal or Amazon, but I’d like to avoid adding a 4th method (counting Bitcoin) if I can.