At Moovweb we've started developing in Go – Google's super-fast compiled programming language. I've really enjoyed working in it, but when learning a new language you are also learning its libraries. Which means tons of time searching through the documentation.
To use it:
The best part is you can also type "package_name#function_name" and the matching function signatures will show up in the auto-complete options. You can easily see whether a function returns an os.Error, too.
To install it, download the package and Chrome will prompt you to install it.
The typing above is something like ten keystrokes instead of 30 + wait time. This makes my productivity OCD happy.