In reply to AndyCook:
You don't need a ledge for the west face of leaning tower, you can bivi on the Awahnee ledge and if you have fixed the next pitch or two you should make the top no problem on the second day. If you don't fancy the rappels late in the day there is a good looking bivi ledge just below the top, or you can bivi right before the rappels (the top of the route is a ridge so not a good bivi spot).
As Enty has said, the south face on washington column is a classic 2 day route where you don't need a ledge. You don't need a ledge for the nose, but it is a big step up from the other two.
You don't need a ledge on the regular route on half dome, this is longer than the column and leaning tower but has much more free climbing.
All of these routes are going to be busy in peak season, basically because they are moderate grade, of excellent quality and you don't need a ledge.