Very few languages are truly groundbreaking. Most are simply refinements of existing ideas (doesn't necessarily mean that they're not a step forward). If you're interested in something earth-shatteringly different, you're going to need to look into programming language research to find it (One great reference that could probably answer this question better is http://lambda-the-ultimate.org/).

For examples of a recent-ish language that was developed by a professor at UIUC, see http://maude.cs.uiuc.edu/, which is based on rewriting logic and is currently still being developed/refined. But even that has strong ties to a previous language OBJ by the same creator.

If you're interested in learning something really different but a bit easier/more fun, I would strongly recommend Prolog. Schapiro has a great book (http://www.amazon.com/Art-Prolog-Second-Programming-Techniqu...).

I got mine right off of amazon - and yesterday I noticed you can buy it straight from the MIT press page as well.

http://www.amazon.com/Art-Prolog-Second-Programming-Techniqu... (if you click on the used link there is a hardback going for 13 bucks right now)

http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&... (they use asp..? regardless brand new hardback for 65)

The Art of Prolog is available new from amazon.co.uk :

http://www.amazon.co.uk/Art-PROLOG-Advanced-Programming-Tech...