Amazon.com has a policy whereby they will refund you the difference of an item that has dropped in price within 30 days of your purchase.
I had no idea idea until I read about it here:http://www.bargaineering.com/articles/amazons-price-drop-policy.html
I was checking my recent Christmas orders and noticed the Seinfeld Season 5 & 6 DVD sets are now $6 cheaper than when I ordered. So I simply used Amazon.com's online interface to request a reimbursement of the difference. I'll let you know how soon the $12.02 shows up as a credit to my account.
Here's the link for the refund page:link
Hopefully the digital camera I bought on December 9th has a sizable price drop before January 8th!
I'm definitely going to be using this Amazon.com feature to help me save more money.