A feature-complete fluent .net library for the Twitter API.
A simple, discoverable, fluent interface for building Twitter queries, as well as additional features like asynchronous processing, server-side caching, url shortening, and rate throttling. Now go, create.
jLinq is a fully extensible Javascript library that claims to allow you to perform "LINQ style" queries on arrays of objects. Really it's a "fluent" notation like LINQ, and isn't LINQ at all, but it's still quite nice.