Here’s a great write-up of current SSBN capabilities and deployments for all the world’s navies. Good stuff.
The current US administration plans to field 1,700-2,200 operationally deployed strategic warheads by 2012; though the lower number is derived by no longer counting the warheads on SSBNs in overhaul as being “operationally deployed.” Two Ohio[s], with 192 warheads each, are usually in overhaul at any given time.
Don’t forget, as the article notes, that the four Trident C4-equipped OHIO-class boomers are being converted to SSGN (cruise missile subs) over the next few years. (Go here and here for more info on that.)