I found this site a while ago...
Dotti's Weight Loss Zone - Restaurants
It is the largest list I have seen, and it seems to have just about any chain restaurant you can imagine. So if where you are going is on the list, this might be quicker than going through the restaurant's web site and downloading a pdf, or whatever.
She has the information for Weight Watchers but seems to have ALL nutritional information for the ones I have checked.
And yes, there are some really useful iPhone apps. But I often found that whatever I ordered was not listed; often the newer "healthy" things didn't show up on my list but maybe that had to do with me not updating frequently enough...
HTH -