Any sites for tweaking system performance?

[budica]

Are there any sites out there that give information on tweaking a system for better graphic performance?

I've just upgraded from a P3 666mhz to an Athelon +2500 and my 3Dmark went from 1000 to 1300, that's not too much. So I want to see if there is anything I can do to fix things up a bit.

Thanks in advanced.