I think the best right now will be rougly 10% off.
I know Target and Circuit City both had a 10% dealio but I think they are both over. Everywhere will charge tax unless you get it from buy.com or amazon.com but even then I'm not 100% sure.
LOL, I'm also about to click the submit button from the applestore. I'm using their educational discount which is $20 off (not quite 10% but close enough), add tax and it comes out to $247.XX shipped. They also offer free engraving.
I am going to just buy from apple store b/c they ship really fast when they have it in stock (not sure if they currently have it instock) and you can't really get any better deals w/ the same amount of hassle (or lack thereof). I know you can do the dealpass GCs and get about 20% off. But again, it's a lot more hassle and waiting.