Look at that: location-based social media service Foursquare has menus now. After adding their Explore feature — which gives you recommendations based on where you and your buddies have checked in — it makes sense to add menus so you don't walk into a recommended restaurant blind. They also added a price level indication logo so you can get an idea of what your wallet is in for. Menus are only on Foursquare's website for now, but they'll be on the app soon.
Yelp added a menu feature back in April, but it's basically just a link the the restaurant's website. (Which accordingly will pop up with a PDF in some cases.) Foursquare hosts the menus on their website, reformatted in their style. Which, let's be honest, is much easier to read than most restaurant websites.
The menus are provided by SinglePlatform, a company that aims to make restaurants more accessible online; they provided Foursquare with 400,000 menus across the country. 250,000 of those are available right now.