Normally this would go in the BE section, since it seems to be the main focus of the site, but I thought I'd let you WG enthusiasts know that one of the current storylines, "Gain", revolves around a woman trying to go from a thin waif of a girl to a BBW. Another one, called "Slime Thief", deals with a woman who can absorb liquids into her body with predictable results.
Honestly, I don't know about the other body expansion sites out there, since my tastes always tended towards BE, but compared to any of those other sites I've tried out Expansioncomics is head and shoulders better and more reliable content providers.
You can see the cover of the latest chapter of "Gain" here:
http://snaketrap.files.wordpress.com/2007/11/08.jpg