Keyboard: get from eBay, its cheaper than iSkin and it covers more area. Had the iSkin for the 1st MB, didn't like it so much. eBay keyboard protector is MUCH better.
Screen: eBay again, I got mine for $10 ea. for both my Macbooks.
Invest in the invisible skin via BestSkinsEver.com
As for case...there's MANY...are you looking for sleeves or hard cases?