Read/WriteWeb had a favorable article recently about a new social network for foodies: iFood.tv. It features the standard social network elements, but also allows users to create, share, rate, and comment on recipies.
I also noticed that iFood.tv is built using Drupal, an open source CMS/building-blocks system with many pre-existing SNS modules. Drupal is a popular and powerful choice if you want to build something custom, but you don’t want to build everything from scratch.