Ok. There is a different between Intel Branded motherboards (which overclock like crap, if at all usually), and motherboards with the Intel chipset. If your board was an Intel brand, then no OC would have been possible.
Currently, motherboards with the Intel P965 Express chipsets are the best overclocking boards for Intel LGA775 CPUs. They have been known to hit an FSB of 500MHz, esp. with Core 2 Duo CPUs. Examples are the Asus P5B Deluxe
for $149.99 and the Gigabyte GA-965P-DS3
for $146.99 However, these boards don't support dual graphics, although the P5B can do so with modded drivers, but with bandwidths of x16, x4.
Second best in the Intel LGA 775 overclocking arena are the boards with the Intel 975X chipset. Here Asus currently rules, but ABIT has a new, promising board. The top contenders are the Asus P5W DH Deluxe
for $249.99 and the Asus P5W64 WS
for $309.99(!!). The ABIT AW9D-MAX
for $239.99 looks promising, but only has one PCI slot which will be useless when using dual video cards. These boards support Crossfire by default, but can run SLI with modded drivers (all in x8, x8 mode).
Now, if you're patient, DFI will come out with an ATI RD600 based motherboard. Here are some images: http://www.overclock.net/1289110-post20.html
This chipset will feature dual x16, x16 PCI-E in Crossfire mode, and rumor has it overclocks well (this is the one I am waiting for...hence my lower-end 975 board). When it will come and how much? Don't know.... Might be worth waiting for and just hold on for now.