I don't buy much on ebay anymore, but when I do, I use esnipe.
http://esnipe10.esnipe.com/
I can go in and put my maximum bid days before the auction ends, and then esnipe bids for me a few seconds before the auction ends. That way the price doesn't get driven up unnecessarily and I don't have to be home to bid.
Years ago esnipe used to be free and then they started charging. I was grandfathered into the free program, so I can bid for free as long as the price is under $25.00. If it's over $25, I use points that add up to some change -- like 25 cents or 50 cents depending on the bid amount.
If I get outbid before esnipe has a chance to bid for me, they send me a message so I can go in and adjust my bid. Usually I don't adjust it. I put my max and if I get it fine, if I don't fine.