I've commented elsewhere in this thread with a list of better articles and papers. If you've only got time to read one, I'd probably read http://research.microsoft.com/apps/pubs/default.aspx?id=1926.... In fact, if you do nothing else, just look at figure 2 from that paper.

Thanks to mjb for the good list. To it I'll add: http://markburgess.org/blog_cap.html

I think I also might write one up myself.

In case anyone is still watching this thread--my version:

http://blog.foundationdb.com/minimal-explanation-of-the-cap-...