Current fastest spec is Corsair Twinx 1024-4400 DDR540 supporting FSB speed of 275. OCZ is about to release PC4500.
But I think you are unlikely to get such a high FSB from and AMD processor.
If your FSB is about 200 or just over then the only gain you can get is from faster timings. Modules based on BH5 will do 2-2-2 timings and hence are the fastest.
Who makes it?
No one, it is out of production.
But you can still get hold od it in modules made by Mushkin, OCZ, Kingston and Corsair, see sticky for details.
br
hepp