I've simplified the interface, fixed a few bugs, and most importantly, added several new datasets to the Milky Way Explorer. There is now context-sensitive help, so you can get information on each map you are looking at by clicking the Help button.
I've tested the interface in Internet Explorer 7, Firefox 3.5 and Safari for Windows.
You can go directly to the Milky Way Explorer here but please read the documentation first if you haven't used it before.