LINQ, the Language Integrated Query, is well known for its ability to query data types like SQL, XML and objects.
However, you may not know that LINQ is extensible — that is, it can be programmed to query data types other than those cited above. For example, there’s a LINQ to Amazon API that will query Amazon.com’s book listings, and interest in LINQ to NHibernate is also percolating.
A third implementation, LINQ.Flickr, will query the popular photo-sharing site. It merits mention today because its author, Mehfuz Hossain, has posted a brief introduction to the LinqExtender tool, available here on CodePlex, which makes LINQ extensibility possible.
You can read Hossain’s LinqExtender introduction here. It sounds like more blog entries about that tool are on the way as well.
UPDATED DEC. 7 — Jonathan Allen over at InfoQ has a recent post introducing the world to Bart de Smet’s LINQSQO, which is a standard query operator that, in taking a deep dive into LINQ, aims to show .NET programmers how LINQ works.