Calibre -
http://calibre.kovidgoyal.net/ can convert a folder into a
single file prc or epub, I've been using it to move them to my iphone,
it's 3am and I'm not quite all there or I'd explain better. It took me
a while to figure out how to load it, but you can mass load and mass
publish, so if you download a lot of stuff, it doesn't take near as
long to input and output it as ebook files. I need to figure out how
the naming convention works, because the way I have my deffnet folders
setup it doesn't read the storyid number and automatically place it
into the ebook information. Other than that, I like it more than mobi
creator so far, as it's a slicker interface.