I ran across this this morning and I thought it might benefit some others.
I use Firefox as my main browser, but I've always had to go back to IE for simple drag and drop FTP capabilities. I ran across this Firefox add-in this morning and it looks to be much better than IE's implementation.
http://fireftp.mozdev.org/ It has more of a traditional FTP client look and feel, but opens up inside of the browser. It also supports drag and drop from Windows Explorer.
Hope this helps a few others out there.
-m@