There were several proposals for missions to Pluto. The earliest I know of were in the plans for the Grand Tour, developed in the 1960s using the TOPS spacecraft design. The Grand Tour would have permitted a gravity assist trajectory from Jupiter-Saturn-Uranus-Neptune-Pluto.
The history next is a little muddy. Four large outer planet spacecraft were planned, under the name Viking, that were to be launched on two Saturn V rockets. Pluto was included in the mission plans, with Jupiter, Saturn, Uranus, and Neptune. I believe the proposed trajectories were Jupiter-Saturn-Pluto and Jupiter-Uranus-Neptune. (In that same time period, large Mars landers called Voyagers were going to be launched on Saturn Vs too. They were down-sized and renamed Viking 1 and 2 and launched on smaller boosters. Apparently names ended up being swapped, as you'll read in the next paragraph.)
The Viking effort to the outer planets evolved into the smaller Voyager 1 and Voyager 2 spacecraft which were launched individually on smaller Titan IIIC rockets. They had trajectories called JST (Jupiter-Saturn-Titan) for Voyager 1 and JSX (Jupiter-Saturn-To be Determined) for Voyager 2, assuming they lasted longer than their primary missions to Jupiter and Saturn. VGR2 was a back-up to VGR1 and would have flown its own JST if VGR1 had not completed its mission or if Titan had been more interesting than was observed at the time (Cassini has shown us that it is MUCH MORE interesting than anyone dreamed). Titan's hazy atmosphere limited what could be done so VGR2 could have gone to Pluto or to Uranus and Neptune. The choice went to Uranus and Neptune, though an acquaintance of mine did run the trajectory long after the decision and found that VGR2 would have had to burrow through Neptune to reach Pluto.
For a more detailed account of more recent efforts leading up to New Horizons, I refer you to http://www.planetary.org/explore/topics/new_horizons/road_to_nh.html. It will recount a little of what I've described and much more about Pluto missions that were proposed but didn't get far along in development.
I cannot cite specific examples of New Horizons technology being used by subsequent missions. What I can tell you, though, is that engineers will always use "heritage" technology if it will do the necessary job. Using heritage technology saves a lot of money in development and testing, compared to brand new technology. You can be sure that New Horizons will provide heritage for instruments or engineering subsystems for future missions.