Nginx 1.4.0, the latest stable release of the popular web server and reverse proxy, is here. It comes with several new features, some of them in testing in the development 1.3.x branch. They're now considered stable and ready for action.
Nginx 1.4.0 comes with support for SPDY, Google's optimized version of HTTP, which will serve as the basis for HTTP 2.0.
It's not built-in by default though, it comes as a module and Nginx has to be built with the appropriate parameters to include support for SPDY.
Also new is support for proxying WebSocket connections. This too has been an option in previous versions, but it's now fully supported.
Finally, Nginx 1.4.0 adds gunzip filtering, making it possible to determine whether clients can decompress gzipped content and unzipping it for them if not.