Price comparison sites.

Allows you to compare many different services and products with many companies.

Money supermarket
http://www.moneysupermarket.com/default.asp?Source=MSBRANDGOO1&section=home&p=0&gclid=CIrglNm28IoCFSdHEAodZWj9kQ

Kelkoo
http://www.kelkoo.co.uk/

Price guide UK
http://www.priceguideuk.com/

Shopzilla
http://www.shopzilla.co.uk/