Camlex.NET simplifies creating of CAML queries for Windows SharePoint Services by using expression trees

This is very good technique when we need to work on CAML queries.
Contributors have done a great job.
Check this for more info on Camlex.NET
http://camlex.codeplex.com/
Check following link for good examples by Sadomovalex for camlex
http://sadomovalex.blogspot.com/2010/06/build-dynamic-caml-queries-based-on.html