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...).

Interesting timing for me -- I've been working through "The Art of Prolog" (MIT Press, 1994) recently -- I'd done some Prolog in school, but never beyond the ``here are a few weeks in a programming languages course'', and the logic programming discussion in both SICP and ``The Reasoned Schemer'' had made me want to go back to the source.

I'm about 2/3 of the way through the book, and I highly recommend it to anyone looking to learn the language in a more or less rigorous way. It won't make you a production Prolog programmer (any more than SICP will make you a production Schemer), but it starts with a firm grounding in the theory of logic programming, and works that up to a good grounding in Prolog step by step, before spending the latter half of the book working through idiomatic Prolog solutions to a bunch of standard (once-standard?) problems (a shell, an interpreter, a compiler), as well as problems more in line with Prolog's traditional uses (ELIZA, an expert system).

The book is here:

    http://www.amazon.com/Art-Prolog-Second-Programming-Techniques/dp/0262193388 

``The Craft of Prolog'', which this post mentions is in the same series, and provides somewhat of a more pragmatic view of the language. I may get to that next. Meanwhile, ``The Reasoned Schemer'' provides the entry of ``the Little Schemer'' series into the field of logic programming, using the MiniKanren logic programming system for Scheme.