Receptional_Andy - 1:07 pm on Jul 8, 2008 (gmt 0)

"in , for , to " for variations of keywords

While there don't seem to be any true 'stop words' these days, it's rare that you'll need to optimise for variations as minor as those, assuming well-thought out copy and reasonably diverse incoming links. You should be able to accommodate those types of variations on a single page.

I would loosely define keyword spam as the unnatural repetition of particular words or phrases.