Well, Excel does have VBA. Whether that's a "normal" programming language depends on your definition of "normal." You can do some very useful stuff in it, but you'll feel like you're fighting the language every step of the way.
1) Spend 3 weeks requesting permission to install your favorite programming tools
2) Look around your Start Menu, suck it up and code it in Excel.
(That is ignoring VB's tight integration, first mover advantage, and the fact that an entire generation of kids grew up coding MS-BASIC.)
For a spreadsheet, Excel's a not-too-bad IDE!
As I was Exceling it up tonight, and I thought to myself if I used Python as the spreadsheet language I'd be quite good by now. Excel feels like an extension of my body - I want Python to feel that way.
To be honest, my first thought was having a Scheme-based spreadsheet. I'm already used to lots of parenthesis and Excel script is sort of functional already. Not sure it'd work though.
I keep thinking that Python(Scheme?) + Spreadsheets = what Yahoo Pipes wishes it was. gDoc's ability to pull from APIs and data functions was a good step as well in this regard.
At least making programming a step closer for noobs like myself.
You may be interested in the "Siag" spreadsheet tool, which stands for "Scheme In A Grid": http://siag.nu/siag/