Feel free to add your own. Give a link and a definition if you want..
Hardware:
http://www.tomshardware.com/ - Nice site, a lot of information, good articles.
http://www.newegg.com - Best site to buy computer parts, excellent customer service and prices.
http://www.anandtech.com/ - Nice site too, a bunch of good articles, trustworthy site.
http://www.gpureview.com/show_cards.php - Compare video cards, gives some detailed information.
http://extreme.outervision.com/powercalc.jsp - Powersupply wattage calculator, gives you an
ESTIMATE on how much watts your computer would need, but it isn't that accurate, considering efficiency and rails matter a lot too.
Software/Programming:
http://www.w3schools.com/ - Good site to learn web programming.
http://www.majorgeeks.com/ - Good place to download freeware and shareware computer programs and utillities.
http://www.cplusplus.com/ref/ - Best C standard library reference out there.
http://php.net/manual/en/ -
The PHP manual.
Anyway, this list is very incomplete, so your help is appreciated