Madshrimps posted an interesting Intel 45nm overclocking guide. Here's an excerpt:

Overclocking always is a matter of eliminating the bottleneck that holds back the best overclock. In many cases, it's either the motherboard or the memory, especially when you're working on a Wolfdale overclock. Basically, it's all about the strength of the northbridge: the more it's tuned for high performance, the less good it'll do in overclocking. The less it's tuned the better for a high FSB. The P965 has been tuned for higher FSB bus speeds because the 975x wasn't capable of it, while the P35 is tuned for higher performance, because the P965 was a bit too slow. Early results show us that the P45 will stand to P35, like P965 stands to the 975x. Very high overclocking results, yet a very low performance rate. The overclocks we've seen above 650MHz are often in combination with 'Performance Level' (which is a memory timing that has the most influence on performance) set to 15. That's like buying a Ferrari when your legs are too short to touch the completely push down the gaspedal: yes, in theory it can go extremely fast, but you won't break speed records driving it.

The main key in FSB overclocks is to unstress the Northbridge: loosening the memory timings, more voltage and colder temperatures. Especially that last factor seems to be working quite good: Liquid Nitrogen on the chipset helps a lot when trying to break world records. Imagine this: CPU, northbridge and 4 graphic cores cooled by liquid nitrogen ... ooh, the extreme overclocking scene will be much more expensive in the future. AND ... Intel is going to release it's E8600 at a very good price anywhere soon: with multiplier 10x. So, we might see 6.5G 45nm action in the near future!