There's an old rule of thumb that says a bear market lasts half as long as the preceeding bull, which makes sense since stocks tend to go down faster than they go up.
So, if you measure the start of the bull from 1981 (which most do) and call 2007 the top, then we should be out of the woods no later than 2020.
Hey, only 8 more years to go!
ebear