Edit: Attachment removed, get it here:
http://www.wowinterface.com/download...85-BagMan.html
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Okay, preliminary version attached to this post. Let me know if anything doesn't work for you and/or it needs more features.
Alt-Click on a bag title to move the bag.
Ctrl-MouseWheel on the title to make the bag frame bigger/smaller.
"/bagman reset" to reset all bag positions and sizes.
I remember someone was looking for an addon to rename default bags a while back, so I might add that, too.