I think that now, with so many people pouring into pharmacy, they're going to phase out the 2 yrs pre-req program. At least that is what my school is doing. I know my school is already changing the 2 yrs pre-reqs to a minimum of 3 yrs for those applying in 2007. I think pharmacy schools would like to see more people to spend more time doing their pre-reqs and preferably get their B.S or B.A before applying.
However, if you still want to do the 2 yrs pre-reqs, I would suggest taking a lot of summer classes if you don't like to have 18+ credits during the regular semester. In fact, my old roommate took 12 hours in one summer before her sophomore year. It also helps if you can clep out and get a lot of credits BEFORE you start college. As others have mentioned, the shortest time you can get your pharmD is 6 yrs but many people take much longer than that.