I an a user of a few of the penny auction sites and it does take some skill and luck to win auctions. I have "won" several auctions, some I got the item for pennies on the dollar, others I only saved a few cents or dollars. The best way to approach these auction sites is to go there with the intention of purchasing an item up for auction (You can purchase it at retail price with the bids you placed being deducted from the final price. That only works on paid for bids. Not voucher bids, which you can bid on as well. I go there with the intention on getting a, lets say a camera. I find one I like, I note the retail price of it (Some auction sites are way over the retail price so do your homework). I purchase that much in bids, and then wait for the auction to start. I will place a few bids right out of the gate, just to see how many people are watching it from the start. That will tell me to either wait a while, or keep on bidding, depending on how many others bid within the "first" final 15-20 seconds (Each site has their own timer set). I have done it several times, and I have not once had to use all my bids and then buy it for "Free" and only pay for the shipping. I always end up getting whatever I want for cheaper then in any store, and have many bids left over to use the next time too.
I only use 3 sites:
http://www.quibids.com
http://www.catchbids.com
http://www.xbids.com
Also a little tip if you are interested. Early in the AM EST (2-5AM) seems to be the best time to bid on something. Things seem to sell for cheaper then say 4 in the afternoon. One site I watched an Ipad 32gb start at 3pm and go until 8pm and sell for $125.00. Another started at 1am and was over within minutes and sold for $0.27!! I kicked myself in the rear for not wanting an ipad bad enough to buy bids for one and start bidding on one, specifically that one ;-)
Anyway, they are money makers for the companies running then, and they do give great deals to winners, if you know how to work the system, or get lucky.