LINQ query expressions that operate on types (monads?) other than IEnumerable<T> -- Possible uses?

Answer 1

LinqToTwitter uses LINQ in an unusual way. Stuff in the 'from' clause is not, logically, an enumerable type. Have a look at the source :)

Answer 2

Thoughts:

• PushLINQ (me and Jon) - reverses LINQ to a push model (rather than the IEnumerable<T> pull model)
• Reactive Framework / Reactive Extensions - another very different eventing model incorporating LINQ syntax
• I wrote a threading API (ab)using the LINQ query syntax; I wasn't 100% convinced by it, so ditched it - but it was interesting; used from (SelectMany) etc to pick out branch/merge points completely unrelated to enumerables