Charlie Calvert's Community Blog : Link to Everything: A List of LINQ Providers
LINQ Providers
LINQ to Amazon
LINQ to Active Directory
LINQ to Bindable Sources (SyncLINQ)
LINQ over C# project
LINQ to CRM
LINQ To Geo - Language Integrated Query for Geospatial Data
LINQ to Excel
LINQ to Expressions (MetaLinq)
LINQ Extender (Toolkit for building LINQ Providers)
LINQ to Flickr
LINQ to Google
LINQ to Indexes (LINQ and i40)
LINQ to IQueryable (Matt Warren on Providers)
LINQ to JSON
LINQ to LDAP
LINQ to NHibernate
LINQ to JavaScript
LINQ to Lucene
LINQ to Metaweb(freebase)
LINQ to MySQL, Oracle and PostgreSql
LINQ to RDF Files
LINQ to Sharepoint
LINQ to SimpleDB
LINQ to Streams
LINQ to WebQueries
LINQ to WMI
http://tomasp.net/blog/linq-expand.aspx
http://tomasp.net/blog/linq-expand-update.aspx
LINQ to XtraGrid