Help with Shopping Engines

[nriddle]

Can you guys please rank/recommend the top four or five shopping engines, in order of popularity? Feel free to chime in also with any comments, either good or bad, on each engine. My knowledge takes me to only these sites:
1) shopping.com
2) nextag.com
3) bizrate.com
4) froogle.com

Any thoughts/comments on each one, in addition to any other good ones?

[pari4]

Here are lots of sites are available for shopping
Such as
Live Product Search
Amazon.com
MSN Shopping
Pronto.com
TheFind.com
DealTime
Yahoo Shopping
Ask Shopping
Ugenie
And so on.