As pointed out, all Athlon 64s have the memory controller built into the chip therefore the FSB link between it and the memory no longer exists, nor does the NB. The technical "replacement" to the FSB is the Hypertransport, a high bandwidth, low latency bus that communicates between the CPU, memory, video card etc.
The Hypertransport will either be 1GHz which will be found on all socket 939 chips, or 800MHz on all socket 754 chips.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w