Threadless Bottom Brackets

If you want to get a decent threadless BB this is your best choice:
http://www.bikepro.com/products/bottom_brackets/mavic.shtml
You will need the BB shell faced but once installed they don't move.
The other big advantage for fixed riding is that they are adjustable so you can dial in your chainline.
I've got one on an old Bob Jackson and it runs very smoothly!
Mavic don;t make them anymore but they pop up on ebay from time to time.

I looked for one of those when my threading first went but had no joy.

@nelson, I have a 110mm axle with shimano sora double and an On one fixed/fixed humb and it gives me a sweet chainline.