JamStudio.com features the Play Page Order, which allows users to have different pages for the intro, verse, chorus, bridge, or any other part of their song.
To play pages in order, enter them into the Play Page Order field at the bottom of the Score panel with commas as the seperator, in this format:
1,2,3,2,2,3,4
To play the song online, any seperator - a comma (1,2,3), a space (1 2 3) or anything else (1w2w3) - will work. But to make a downloadable mp3 file with the MP3 Mix feature, a comma is required.