I'm a tiny bit hesitant to recommend this but it worked for me. I was able to get a new-in-the-unopened box T61 with a 2.4GHz cpu, 160gb HD and a 6-cell battery for $645 delivered this week.
First, go to
http://live.com (it's a Microsoft website) and sign up for an account. Sign in and do a search from there for T61 or whatever you would like.
The first item that will come up at the top of the list will be eBay and there will be a small banner that says "Live Search Cashback" - the amount seems to vary from 20-25%.
Clicking on the banner will take you to eBay. On the left side of the screen, choose "Laptops and notebooks" so you don't see everything that happens to have T61 in the name. Under "PC Laptops Finder", again on the left, choose your configuration. I just had it show everything that was new-in-sealed box.
When you check out, the discount will be deducted from the final price, not including shipping.
That's it. But...you are not bidding on an auction, only buy-it-now items are eligible. You must pay with PayPal. Microsoft will hold your discount for 60 days in your Cashback account and send you a check or deposit it in your PayPal account after that time.
The maximum discount is $250 per transaction and you have a three transaction limit.
It does seem a little fussy and I'm sure there are several of the details that could wind up being deal-breakers for some but it worked well enough for me to use all of my three transactions this week.