Tag List Control

[AbbottF]

I'd like to suggest a Tag List control similar to the way StackOverflow handles tags. When displaying tags they should look like ...

When they are being selected from a list, they should display like this, giving the ability to easily remove them ...

In my needs, the tags are all predefined and in the 100s. In control users should be able to add new tags on the fly. Not sure of the behind-the-scenes storage issues.
Tag selection should use IntelliSense and could display in the form of a dropdown or an alphabetic tag list display.