I've recently updated the list of LINQ Providers found on my Links to LINQ page, accessible from the News section on the left of this blog. I'm sure there are other providers available. Feel free to write me or append a comment if you want to add to this list.
Below you see the current state of my LINQ providers list, as of Feb 28, 2008. I will maintain this list on my Links to LINQ page, so check there for updates.