This is quite a slick little library that looks like Chosen but does a bit more. I like keeping links like this in my pocket as new projects come up. I specifically keep an eye on the changes version to version to try and get a feel for the overall stability of the project as a whole.
I’m impressed with the documentation and feature set of Select2, and I can only imagine we’ll be seeing it crop up among Web apps, plugins, and the like over time.