We bought the Serta Beautyrest for baby's crib...because we have the King size one and it is comfortable. BRU carries it and with a 20% coupon it is a good value. Reg price $200.
I also recommend the Moonlight Slumber - you don't need to buy a matress pad and it is super light because there are no springs. Makes it easy for those late night sheet changes!
Re: Please recommend your crib mattress
Colgate Classica III (Dual Foam) $150 on Amazon.com
(I was given the option of ANY Colgate mattress - the son of the owner of the company suggested that one!)
This is the exact one we just ordered. It has great reviews.