Motherboard

Many vendor to offer you, like : asus, asrock, abit, iwill, Gigabyte, msi, AOpen , Biostar, DFI, jetway, freetech, pc chips, krypton, leadtec. etc.
example :
for amd processor :
abit NI8 SLI Socket LGA775, with : NVIDIA nForce4 SLI, FSB 1066, PCI-e x16, SLI, SATA 150, RAID, GbE NIC, USB 2.0, Audio, S/P DIF, DDR2 667, Dual Channel, Abit µGuru™ Technology
or more cheaper
ABIT SG-80 : Socket LGA775 with , SiS 661FX, FSB 800, AGP 8x, SATA 150, RAID, NIC, USB 2.0, Audio, S/P DIF, DDR400 .
not only this vendor for amd much more you can find it : asus, aopen, iwill,asrock,ecs, jetaway etc.
example For Intel processor :
ASROCK 775Dual-915GL Socket LGA775, Intel 915GL, FSB 800,PCI-e x16, AGP 8x, VGA, SATA 150, NIC, USB 2.0, Audio, DDR400, Dual Channel.
or more expensive
ASUS P5LD2 Deluxe : with ; /WiFi TV-Edition Socket LGA775, Intel 945P, FSB 1066, PCI-e x16, SATA 150, RAID, GbE NIC, USB 2.0, Audio, S/P DIF, DDR2 667, Dual Channel .
not only this vendor, like amd too, for intel processor had many vendor you can choice, like asus, asrock,gigabyte, pc chips, etc.

what you motherboard choice, must be macthed with cpu (processor) for AMD or Intel, you can find the right price for your budget.