I'm really having fun overclocking this board right now and starting to get some great scores on various benches.
I'd like to point out a few BIOS features that, while not unusual to tinker with, tend to be ignored in discussions of voltages/baseclocks/multis.
This is the G25 BIOS. I haven't tried P08 yet, so I don't know if much of this has been incorporated yet.
Please don't pay much attention to the various multipliers in the first shots. They are with the i7 975, and you won't have as much freedom with them with 920's and 940's.
OVERCLOCKING AND OVERVOLTING VOIDS YOUR WARRANTY AND CAN RUIN YOUR HARDWARE. BE FOREWARNED THAT THIS TRUMPS ANY OTHER "ADVICE" I SUPPLY.
The pertinent G25 change here is the PCIE frequency at the very bottom. Upping that to 101-103 can get you higher baseclocks. Be warned, higher PCIE frequency can affect your system and is particularly hard on HDD's. On the other hand, increasing to 103 isn't that big of a deal. 115+ like you can do on other boards (or this one if you are inclined to solder tiny transistors) can ruin your HDD's.
I forgot a screenie, but if you go into OC Gear it allows you to adjust your skews. I've found it useful to put IOH and CPU skews at 100-200 ps at clocks over 4.5 ghz (or 400-500 ps at 5+ ghz ranges).
Brief mention of voltages. (Ignore the numbers I have in there - this is on Dry Ice and Liquid Nitrogen cooling). Most of you should know that it is very important to keep VTT and DRAM within 0.5v of each other to prevent damage to your internal memory controller. This rule is where the 1.65v limit for RAM voltage comes from (on my i7 920 default VTT was 1.15). If you are increasing your VTT, then you can increase your DRAM (at least as far as the IMC is concerned - your RAM itself is a different story - but most can tolerate up to 1.85 without much trouble).
PLL changes can sometimes help, but usually don't do much of anything.
I have personally found that increasing IOH (northbridge) and ICH (southbridge) voltages help tremendously with stability. Don't forget to try the ICH if you are having stability trouble. One really nice thing about the bloodrage is that the chipset cooler heatpipes are set up so that the southbridge and vregs can benefit from using the NB waterblock.
RAM timings. Often overlooked, but extremely important. If you are having stability trouble, consider loosening your timings. Often, your RAM is limiting your overclock. There is lots of discussion all over the place on the main RAM timings, but the main feature I'd like to point out here is the tRFC. Making it greater than 74 can really improve stability. But doing so can reduce performance.
CPU features. If you use turbo, leave EIST and PPM enabled, but disable CXE. HT on or off - lots of controversy on that all over the place. Enabling TDC and TDP and setting the max to 32767 will prevent your multi from dropping under heavy load. (even if you have turbo "always on"). This apparently has been fixed in the P08 BIOS so you may not have to change these anymore.
Increasing drive strength and latencies can improve your high baseclock overclocks (as in 215-220 baseclock and above range).
I hope that helps some of you. I just wanted to touch on a few settings that I rarely hear mentioned, but can make a big difference with higher stable overclocks.