... couple of smart tools I use for shopping on Amazon or Ebay (UK but I'm sure there will be equivalents available locally.
One is this rather handy Amazon Discount Finder from Martin Lewis. It searches and finds products with great discounts for the criteria you enter. It's free so give it a whirl. I use it all the time...
Secondly, you may or may not be familiar with ebay snippers. What they do is automatically place a bid for you on something a few seconds before the time runs out. There are many out there but I find this one to be reliable. It used to be Goofbay but they've just gone through an overhaul and re-emerged as Goofbid. I've already successful placed some bids with it's new incarnation so nothing has changed in terms of functionality. Again, it's free to set an account up and can save you money by not getting into a bidding war. It's simple to use and self explanatory.
OK, not really about making money... but will save you some.