Been looking for this for a while now, how good are we at documents on how to take your XFN scripts and play with your XML heebeegeebeees....well yes actually rather good. So I liked this site because it's simple:

Why doesn't more of our stuff start off with a nice 'Basics' overview - great to see the office team setting the standard. Check it out if you want to see the basics on Excel Services.

Enjoy!