BBC World News has an outdated article that addresses at least part of your question. According to the article, the U.S. has 12,070 warheads. This figure probably includes tactical nukes, such as field artillery shells and short-range missile.
This site, based on 2003 figures shows lower numbers for strategic nukes: 8,855 (7,000 active, 1,855 inactive), tactical nukes: 1,600 (800 active, 800 inactive), making the total warheads: 10,455.
This site gets a bit more specific, showing 2000 warheads on 550 land-based ICBMs, 3456 warheads on 432 SLBM on 18 Trident submarines, and 1750 bombs for 72 B-2 and B-52 aircraft for a total of 7200 warheads with 1074 launchers (including aircraft).
More info here.
The Russians are supposed to be committed to reducing their 28,000 nuclear warhead (peak) inventory to 1500 by 2007, but they are lagging behind that considerably, probably dragging their feet because the U.S. isn't doing much to reduce it's nuclear inventory either. In the past year or so, both sides have been talking up new weapons systems leading me to believe we're not headed in the direction of disarmament at all. Given all that, I'd say most of the U.S. missiles are still designated for Russia, and probably a sizeable number for China. I suppose with today's computer techology, retargeting any of the missiles should be quite simple and quick.