VSelect
This is a tool for managing a Mugen select screen using a visual drag&drop interface.
It's an alternative to editing your select.def file in a text editor; it allows you to easily add, remove and arrange your characters, assign them stages, etc using a mouse.
It's compatible with all versions of WinMugen, Mugen 1.0 and 1.1, and supports zipped characters. More details and discussion here.