Greasy Fork is available in English.
Enhancements for Facebook: bigger profile pictures and photos, easier viewing of albums, links to download videos, showing people's age and sign, google calendar integration, keyboard shortcuts & more. Compatible with new Facebook and fully customizable!
Features, control, customisation?
There is no hint in the description of what level of control a person might have over the performance. There is no screenshot. These things would be handy.