Also seen on the db4o community, but it could be of interest to everybody: http://developer.db4o.com/blogs/carl/archive/2008/05/02/linq-for-java.aspx
Old post about Java and LINQ.
Carl (db4o's CTO) would really like to start this initiative, as an open source development, as a JSR and as an Eclipse plugin. A Google group has already been started.
Please note IBM PureQuery (as part of their Data Studio) has some sort of limited support for LINQ. USed to be known as JLINQ.
Quaere, another limited LINQ for Java implementation, hosted on CodeHaus.
Jonathan Bruce's post about Quaere.
I've also seen that one: JoSQL.
Charlie Calvert's links on LINQ. At Xcalia, we enjoyed working with Charlie's team in the TAP program in 2007, mostly around LINQ.