Salsa is the name of the collaborative development server for Debian and is the replacement for the now-deprecated Alioth service.
To make it easier to show the world that you use Salsa, I've created a number of Github-esque ribbons that you can overlay on your projects' sites by copying & pasting the appropriate snippet into your HTML.
For example:
You can find them, with instructions, here:
If you're not satisfied with one of the colours, the original source is available.