[OT] functional programming resources ?

[Mariusz Gliwiński]

Hello,
could You recommend me some books / materials explaining different 
concepts in functional programming from *practical point of view*?
Most preferably not requiring me to understand Haskell or other 
classical functional language.

I'd like to try it with D.

I'm using more functional style overtime, but i'm afraid to rely on 
compiler optimizations so highly.
Anyways, i don't feel like i could write big part of my code pure && 
functional yet, so i'd like to learn about it at least a bit more.

Thanks,
Mariusz Gliwiński