[Babrbarossa]

Some overclocking guides from around the net:

Here is one released in March/07 which is a quick and dirty guide to overclocking the e6400 by Legion Hardware- A must read for any new C2D overclocker.
http://www.legionhardware.com/document.php?id=625&p=0

A very good one made in Summer 2006 from devhardware forum:
http://www.devhardware.com/forums/cp...ing-97163.html

Part 2 of Tom's overclocking guide entitled - suggested components and settings. http://www.tomshardware.com/2007/01/..._guide_part_2/
here's part one from tom's
http://www.tomshardware.com/2006/12/...-guide-part-1/

here's another from tom's for an e6400
http://www.tomshardware.com/2006/10/...lls/index.html

here's a brand-spankin' new one for e6300 from legionhardware
http://www.legionhardware.com/document.php?id=606

here's an ok one from the forum at anandtech specifically for core 2 duo
http://forums.anandtech.com/messagev...readid=1947261

here's evga's official overclocking guide for the 680i-- VERY useful if you have this mobo, but a fairly large pdf file.
http://www.nvidia.com/docs/CP/45121/...erclocking.pdf

...and another specifically for c2d and the 680i-- I like this one.
http://gear.ign.com/articles/747/747671p1.html

Here's a couple for the 680i from the evga website:
one quite comprehensive by [p]wnzer:
http://www.evga.com/community/messag...TOPIC_ID=25883

and one quick and dirty by ironkidz:
http://www.evga.com/community/messag...TOPIC_ID=23999

here's one that gives an ok background
http://www.xtremesystems.org/forums/...ad.php?t=57148

here's a good sort of faq
http://www.xtremesystems.org/forums/...d.php?t=114824

here's a good guide if you want to play it safe (bumping each value up in small increments) I personally like the speed of setting voltages fairly high at first and bringing them down.
http://www.ultimateoc.co.uk/Forums/v...a5d8d88341c25a