Take a look at http://factorcode.org/ - it's very Forth-like, but has a lot of modern constructs. It's very active and the (core) libraries are quite stable.
Having never played with Forth-like languages before, I'm finding writing even the simplest algorithms strains my mind -- in a good way, though. It's mind expanding in the same way Lisp was the first time.
I doubt that Factor is the next big thing, but I think that for smart people it's one of the most fascinating things around right now. Zed Shaw, for example, is a big fan:
All that said - I've never found it 100% natural, but (perhaps paradoxically) on the other hand I'm usually pleased with the results.
http://img301.imageshack.us/my.php?image=addtobinarytreescre...
It is shown compared to the analogous code in C++ and Lisp.
My Factor version could probably be improved. In fact, I just now realized that I could have factored out the two final calls to <node> into a single call.