i'd brush up the design usability. you're on the right track, but i'd avoid the float right/left on the form labels/inputs respectively on a flexible layout, because it makes it harder on the eyes.

also, perhaps set a cookie or something to allow someone to possibly go back to their last created dropbox from the main page. would be more convenient for the people who lose their urls. and/or an option to enter their email address and have the urls emailed to them, and maybe new comments.