The only visible answer (before this) lists only SE sites. Any question closed on SU as off topic is likely to be closed as off topic on any other SE site, otherwise would they not be transferred there? At any rate, all SE sites have a FAQ and I'd wager all of them state they don't allow shopping questions. So whats the use of redirecting "shoppers" to other SE sites?

Computer-related shopping:

• www.newegg.com (US based online store)
• tomshardware.com (publishes reviews and charts, not sure how interactive they are)