Latest stats are always a little dated and behind the real world, but as of the end of June 2007, looks 84% of US households have Internet access, with 75% of all US households having broadband access.
Those without access at all are not as likely to get it, 'cause they don't want it. Most on dialup are the less-than $30,000 per year households, or the live in rural areas where cable and DSL is not available. (We have a satellite at the house out in our neck of the boonies).
The majority of those without Internet access in the home have it at work, school, the library, Internet Cafes, etc. The glaring exception is the elderly, who, if they don't have it in the home, don't have it at all.
Slow and steady, even in expediting, wins the race - Aesop