Hi.
Like PT says it depends on how will you use the PC.
But you may want to try rhis:
>> not neccesary a super-duppa CPU, if you want your PC for gaming go for AMD like X2 series, 4600+ or better or if you want to minimize costs you may want to buy a cheaper version and Overclock it, like the X2 3600+ brisbane can OC very well or the X2 3800+ can OC till 2.8 GHZ (like a X2 4800+). Or you can buy an Intel Core2Duo that OC very well too, but note that these CPUs are more expensive.
>> RAM like Ballistix, OCZ, Kingston, etc. Depends on what you want to do with your PC, if you'll use it to OC purposses you need a 667 or 800 MHZ versions and a model that you know it supports the OC........but at least 1 or 2 GB in PAIRS (2 X 512 or 2 X 1GB) to experience the dual-channel features.
>> The Mobo....this item is very important since it the source of the PC's resources, again, if you will not make OC almost any model of any brand will bring you descent performance, but if you require for gaming or OC you must buy a descent model like S4 series of Gigabyte or Deluxe models of other brands, make ASUS or GIGABYTE your first choices.
>> And the last, the VGA card, if you dont want your PC for gaming.....well, it's not neccesary to buy it, other way, try to buy a 7600GT or better for Nvidia or X1650 Pro or better for Ati.
The trick to save your money is ONLY fill your needs and nothing more, for example: if you buy a Intel quad core + 4 GB ram + Nvidia 8800 ultra + super-duppa accesories JUST to do Homework and web surfing.....IT SIMPLY DOESN'T MAKE SENSE.....got that?
Hope you will find it usefull.