Full disclosure up front: I currently write for ExtremeTech and Hot Hardware. In the past I've written for Ars Technica (2007 - 2009) and briefly Tech Report (2H 2005). Before that, I wrote for a now-defunct site going back to 2001.
Obviously I could be biased and plug the sites I write for. I write for them for a reason, after all. But since no one is going to buy me telling you to read my own work, here's where I go, personally:
For in-depth, excellent analysis (in alphabetical order)
Anandtech (Anandtech.com)
Ars Technica (Arstechnica.com)
Tech Report (techreport.com)
For ultra low-level analysis:
Real World Tech (www.realworldtech.com)
Agner Fog's CPU blog (www.agner.org)
Lost Circuits (www.lostcircuits.com)
All three of these resources update only occasionally. But the information is second to none.
For spot-checking or specific issues:
TechSpot.com does great CPU/GPU scaling articles. LaptopMag or NotebookCheck are great for their particular areas. CPU-World has good general database information, VR-Zone often has interesting scoops, as does wccftech -- if you're willing to filter out a lot of rumor / speculation from the latter. Tom's Hardware has useful dynamic databases for product performance. So does Anandtech.
Don't be afraid to read a review on a site you haven't heard of, or with a layout from 1999. While established names and high-quality writers tend to go together, they are neither exclusively matched nor guaranteed. A good reviewer will document issues, give a thorough discussion of the topic, and won't come off sounding like a marketing employee.