It's always very enjoyable and quite productive when Cairo developers can get together and accomplish some tasks. This often happens informally, when various Cairo developers happen to be at the same conference, such as has happened with the GNOME Summit, LCA, GUADEC, GTK+ HackFest, LGM and other occasions.
More recently, the idea has been proposed to specifically invite and gather together Cairo developers for a meeting whose sole purpose is to improve Cairo. (These gatherings will always be open to any interested developer - just space may be limited and priority will be given to active contributors.) If successful, perhaps this will become a more regular event. For now, see the following pages for more details on specific events:
Hackfests
These tend to be more local affairs, organised more informally when a few developers can arrange to meet at a particular conference. Anybody who has a problem to solve or an idea to share is welcome. The goal being a sprint to improve Cairo.