I put this Sette Amp saddle on my MTB last year and freakin love it. Its about 1/2 the size and weight of the WTB saddle it came with and is much more comfortable.
http://www.pricepoint.com/detail.htm?stylepkey=15965&style_id=270%20SETAM7&detailName=Sette%20Amp%20Saddle
No-one suggestion Specialized Body Geometry.
I've got one. Simply the best saddle I've ever had. They measure your sit bones so you can determine if you've got wide sit bones or skinny ones.
Mine are wide. The seat is the widest available. Still pretty light, but its comfy.