The below are suggested reading if your looking for some good info on various computer related things.
I also recomend having a look at the Benchmark Photoshop test, and running it yourself.
The 4GB FAQ explains a lot of things people should know, especially as the world is slowing moving towards being 64bit, and camera resolutions continue to increase.
Please feel free to suggest any threads that should be added here by PM'ing myself or another mod.
But please don't reply to this thread The Whats your computer build thread is a great place to get ideas if your into building your own.
Digital Photography with Linux: Reference Guide
Benchmark Photoshop Speed Test
-=FAQ=- Why don't I see all my RAM? The 4GB limit. --> for 32 bit Windows systems through XP. May not apply to Vista or 7 32 bit versions.
Windows 7 and RAW plus 64bit info
The -=Official=- Graphics Workstation Tweeking thread
Microsoft Vista Compatibility Issues
Mac Users - Snow Leopard
What's Your Computer Build?