All knows the famous and important online auction and shopping website Ebay.
On net there are reliable services and programs that allow to automatically bid at last seconds and allows to win them.
I list here some secure and mainly totally free:
JBidWatcher, written in Java (so it needs relative runtime libraries) and available for Windows, Mac OS X and Linux.
Biet-O-Matic, for Windows, Firefox plugin available too.
GIXEN, web service, so totally online without need install a program.
Finally a comparison chart of the various services/programs not just for the price but it contains also other useful information.