One program that will surely be most sought after on the web today would be auction scripts. Many sites from all over the world have been looking for scripts that can offer a similar flow that eBay and Amazon have been offering although to a different degree.
Ranging from bidding all the way to multiple payment modes, the various features that auctioning systems such as the PHP Pro Bid is surely something that can prove to be beneficial to both the owner and the market he wants to get over the web. Definitely something aspiring business makers on the web will have to check out.
(Source) PHP Pro Bid