Today, we're adding an "Extensions" link to the Google Wave navigation panel that gives you quick access to a set of fun and functional featured extensions for waves. The gallery is simply a set of waves containing extension installers (the puzzle pieces). The first wave, " Read me first " contains an introduction to extensions and how to use them. We released Google Wave to the developer community first back in May 2009. We did this because we wanted them to help complement the product's core features by building rich extensions. When we launched our preview in September, we featured some great extensions and prototypes , like AccuWeather's forecast gadget , LabPixie's competitive Sudoku game and even built a couple ourselves, like Yes No Maybe and a Google Maps gadget . Since then, many more extensions have been built, and we want to make it easier for everyone to discover them. Just click the link to browse some featured extension installers.…