ResolverOne is one of my favorite applications in the past few years. It's a spreadsheet powered by IronPython. Spreadsheets are among the most powerful intellectual tools ever developed: if you can solve your problem with a spreadsheet, a spreadsheet is probably the fastest way to solve it. Yet there are certain things that spreadsheets don't do well: recursion, branching, etc.
Python is a clean, modern programming language with a large and still-growing community. It's a language which works well for writing 10 lines of code or 1,000 lines of code. (ResolverOne itself is more than 100K of Python, so I guess it works at that level, too!)
From now (Dec 2008) to May 2009, [Resolver Systems is giving away \\(2K per month to the best spreadsheet built in ResolverOne](https://www.resolversystems.com/). The best spreadsheet received during the competition gets the grand prize of an additional \\)15K.
Personally, it seems to me that the great advantage of the spreadsheet paradigm is a very screen-dense way of visualizing a large amount of data and very easy access to input parameters. Meanwhile, Python can be used to create arbitrarily-complex core algorithms. The combination seems ideal for tinkering in areas such as machine learning and simulation.
I try to do some recreational programming every year between Christmas and New Year. I'm not sure I'll have the time this year, but if I do, I may well use ResolverOne and Python to do something.