LGA775 CPU's have no-pins on them (the pins are on the motherboard)
478 has pins on the CPU and the socket on the board.
almost all 775 motherboards support single and dual channel ram configs.
478 motherboards support Dual channel also, not all do, but most do.
Just for FYI, LGA775 is cheaper and packs more performance. But you will be forced to use PCI-Xpress if you do not get a mobo with the Intel 865 chipset. Only the 865chipset supports AGP to my knowledge.
INTEL i7 930
3x2gb Corsair Dominators
EVGA GTX 480