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.

I've been toying with Factor for about a week. It's been an enjoyable experience, as both the language itself and the included development environment are extremely well designed.

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:

http://blog.cusec.net/2009/01/16/zed-shaw-on-factor/

Yeah - Forth and Forth-likes encourage an extremely modular, concise, expressive form of coding... When you add macros it gets some of that meta-programming feel that comes with Lisp.

All that said - I've never found it 100% natural, but (perhaps paradoxically) on the other hand I'm usually pleased with the results.

No kidding! Take a look at this code I wrote for adding a node onto a binary tree:

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.