What's the easiest way to implement (something like) Gmail's interface for labeling messages? Does any javascript library have a widget like this?
http://img294.imageshack.us/img294/7097/36698396.png
Behavior:
Horace - you want something really complicated, and you should take into account that even with a lot of pre-made component, it will take some time to get something like this working (not to mention - being pretty :-) ).
Anyway, pre-made components are nice but I often like to hack it myself, free-style like. So here is something I cooked up to get you going: My simple label demo (warning - I only tested this on Firefox 3 and I'm pretty sure that it won't work in anything else).
It is far from being pretty, but the code is pretty straight forward and should be easy to understand.