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I'd recommend a "c" series northwood over the "e" prescott, due to heat issues. The 2.8 or 3.0c are good choices for performance and value. You can use them with the abit is7 or ic7. For amd, the socket 939 3200 is a good choice, if you can find an nforce4 board to go with it. If you don't have deep pockets, I would get the non sli version and save about $80-100.

Im not that technical with PC parts all i know is that the CPU i stated is a fast and in my price range one its around 120 pounds

For socket 775, checkout the abit AG8 motherboard with pci express and regular ddram support. Regular ddram is cheaper than ddr2 and performs just as well. Some of the new Intel heatsinks are rather loud. I use a zalman "fan mate 1" to reduce fan rpms for quieter running. It's only $5 in the us.

From what everyone says LGA775 is fairly fragile so make sure u know what your doing b4 u install the chip.

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If you are going with a 3.0 CPU stay away from the Scoket 775 and get the Socket 478 flavor. Heat is a big factor with 775 CPU's. Im not knocking the 775, I have the 3.4 CPU and really like it. I am running a liquid cooling setup to deal with the heat so if your going to use a 775 CPU my suggestion is to do so only if your going to get one of the faster models and you plan on using a liquid cooling system. If your staying in the 3.0 range then I can really see no reason to deal with the issues that come with the 775. As one of the other posters stated, this is a very fragile setup and can easily be damaged if not handled properly. Personally I own a 3.0E socket 478 Prescott and the 3.4 775. The 3.0E is hot but not as hot as the 3.4, but if I were buying the 478 agian I would look for a Northwood "C" series as these are the coolest of the 3.

Stick around, and read for a while before you buy.
Warning, smart people who do that usually end up getting an A64 amd chip, because it is cooler, faster for gaming, and a little cheaper.
Most people around here will agree that Intel made a mistake with the prescotts, while Amd has done great with the A64s.

Sockett 775 Chips are great IF YOU COOL THEM WELL. Make sure to get an aftermarket cooler, i'm using the Zalman CNPS7700 and getting great temperatures, esp if you don't plan to OC, or aren't going to OC to the extreme.

You'll hear often that the LGA775 prescott's put off alot off heat, and they do, but they are well managed with a good cooling system. So if you can afford that, don't rule it out just because of heat.

Also, the LGA775 system is not as fragile as has been first reported in the computer world. I read an article where one site replaced the CPU over 200 times with no problems. And i personally fuddled the pins accidentally when installing a temperature monitor under the CPU, and there weren't any problems. No bent pins or anything. I wouldn't recommend trying that tho  .
NOTE: i got an expensive High-end motherboard from Asus tho, so i don't doubt that it may be sturdier than others.  

ONE NOTE OF CAUTION: MAKE SURE YOU GET AN E0 STEPPING PENTIUM 4 PRESCOTT, if you decide to go LGA775. They handle the heat much better. They are noted by having the letter J after the number, I.E. Pentium 4 550J.

I can't speak for AMD chips tho, you'll have to ask some of the other guys here for more info on those. But i have been happy with my LGA775 system.