I created a couple of new videos to talk about space switching and space matching. I think they're pretty self-explanatory, just going over the basics of what they are and some ways to set them up. Nothing too crazy, though the space matching one is a fair amount of python scripting (though again, nothing terribly hard if you're already using python).
But if you're into the more complicated bits, here are some links to info about them:
Charles Looker - http://charleslooker.wordpress.com/2012/02/25/multi-directional-constraints/
Hamish McKenzie - http://www.macaronikazoo.com/?page_id=413 (very illustrative, but be warned, some of his matrix math stuff used his own scripts to deal with the matrices, so it can be a bit confusing if you try to do it without installing his scripts first. But the principles are the same, I just use the API to do the matrix-y bits, which can be hella confusing in it's own right)
TD Matt - http://td-matt.blogspot.com/2010/12/broken-hierarchy-rig-and-space.html
Oh yeah, and the vids by Jeremy Ernst are here: https://vimeo.com/jernst. Good stuff!
And I'll say it just so you don't have to. . . My god am I long winded! Not sure how explaining space switching could possibly take that long. But what can you do? :)
Maya/Rigging: The basics of space switching from zeth willie on Vimeo.
Maya/Rigging: Space Matching from zeth willie on Vimeo.