I remember about 2 months ( maybe more? ) ago an MS guy contacted me about using one or more of my controls to do a many-to-many relationship UI in a datagrid for some unknown web app project he was fiddling with. At first we talked about using a CheckedListBox, and doing a whole buncha code to select/unselect stuff. After pondering that for a while, he decided that he'll use DynamicListBox to make a two-listed UI with add/remove buttons. You can see this type of UI in action by rightclicking the IE toolbar, and choosing customize.

Unfortunately, I've since lost his address in an inbox purge. This is unfortunate because I've actually gotten around to creating this UI, built into the same assembly as DynamicListBox, called DualList. So hey, unknown MS guy, in the extremely rare case that you both:

1) read my blog, and
2) are still fiddling with that app

go take a look.

I'd always told people that inquired about me developing this control that it'd be rather trivial to make it, based on the dynamiclistbox, and while it wasn't as trivial as I'd assumed... it was kinda neat. It's actually the first useful control I've made that built upon a previous control of mine, when I didn't even have the new use in mind when I originally built it.