Resources to evaluate performance of PC parts
Quality review sites
Databases and miscellaneous
Resources NOT to use to evaluate performance
These websites primarily use Synthetic Benchmarks 1 for comparisons (at this point its better to consider sites terrible until proven otherwise) and as a result do not reflect real world performance 2 as well as use statistics like clock rate 3 that have no legitimate usage within this scenario. Other sources should be taken with a grain of salt and evaluated against 4. These sites also tend to suffer from unregulation of results, verification of results and self-selection bias.
http://gernot-heiser.org/benchmarking-crimes.html (Thanks ZeDestructor)