Because there are only so many human beings 6'8" and taller, and because every competitive basketball team needs a handful, the following bigs will draw ample interest on the 2012 trade market.
Warm bodies, long legs, will travel.
Now, within the spectrum of big and tall, there are varying levels of usefulness.
The following list of top bigs available this season* intends to parse that spectrum, separating the large and talented from simply the large.
*For the purpose of this list, I excluded players who are available only in a specific trade scenario (i.e. Andrew Bynum for Dwight Howard). We're only considering players who are available in a more general sense.