While there are a series of different bb types that have been used over the years, the only one in real widespread use is the British, or ISO (of course this makes sense because ISO stands for international standard). Because the right cup is left hand threaded and the left cup is right hand threaded, the force exerted by the bearings on the bb shell serves to slightly tighten rather than loosen the bb cups. A few hyper-traditional italian road frames may still have the italian style, bb both cups right hand thread. This is really not a problem because if a builder is foolish enough to still use an italian bb shell you probably don't want the frame anyway.
More interesting is the return of the perenial interest in press fit systems in mountain and road bikes. Cannondale is already using an oversized shell/press fit bearing combination in their high end road, tri and mountain bikes, while FSA is pushing a standard (ala ISIS) called mega tech www.oversizedbb.com
. Of course press fit bb's are nothing new Klein tried it a while back and it is the method of choice for most BMX bikes. The big advantage is the use a larger diameter aluminum spindle to reduce weight and add stiffness. There is also the advantage of an increased weld area on the larger bb shell and larger more durable bearings. The big problem is istallation issues, special tools and a need to have a perfectly faced bb shell. Ironicly just as press fit systems are gaining popularity for road and mountain, the hard core BMX riders are abandoning them for the easier and more reliable ISO bb (or EURO as they call it in BMX).
Hopes this helps