A good bike shop should let you try several different saddles on your bike before you purchase. Also, make sure you adjust the position (forward/back) and the tilt (up/down) to get it right. If you ride for a bit (just a few minutes on a fit trainer) and when you get off, the blood starts rushing back to your privates then it's not properly positioned. So even a great saddle, adjusted improperly can be uncomfortable or leave you numb.

I know each model is different and each butt is different. but the two saddles I've found most comfortable are the Sella Italia Ladies saddle and the Terry saddle (I tried the pink, breast cancer saddle on for size, but they have other colors).

Terry: http://www.terrybicycles.com/saddles...?item_no=21635
Sella Italia: http://www.selleitalia.com/eng/index.html

Have fun!