Easily discover if you can donate to or pay for something – perhaps a blog post or open source project – through a button in your address bar.
By detecting the existence of rel-payment links on a page a button is added to the address bar linking to the page where you can donate or pay for the current page.
Rel-payment is a standard used by eg. Flattr and Gittip and links to these two are also specially indicated by showing a green or brown button rather than the ordinary golden coin button.
Flattr's official WordPress plugin is exposing rel-payment links for all blog posts making it not that rare to find blog posts that you can donate to through this button in the address bar and with the button always appearing in the same place it is very easy to find it compared to having to look for it somewhere within the blog itself.
This add-on is very similar to the official Flattr add-on, sharing some basic components, but unlike that add-on this one makes no external requests to any API:s and can detect non-Flattr links as well.
Source code is published on GitHub.