There doesn't seem to be as much turnkey rails stuff in use as there is PHP (or perl) stuff across the board. Other examples would be phpBB or phpMyAdmin and vBulletin.

I wonder if part of the gap is perhaps cultural. Rails comes out of 37 Signals who made lots of money doing Saas so they are going to be something that rails developers naturally aspire to.

In an instance where a PHP developer might say "I can make this software, I'll put it up as OSS or I'll make it commercial and charge a fee to download it" a rails developer might think "I'll stick it up on my own servers only and charge people a monthly fee to use it or have an ad supported model".

In other words , rails people may just be a bit more entrepreneurial. PHP also grew up in an age where you would probably be considered a bit crazy to do all your project management on the web.