I'd like to see a series of interstellar precursor missions,
with each probe building upon the technology of the previous mission. Start out with a 100 AU probe, followed by 500 AU, 1,000 AU, and 10,000 AU missions. The 100 AU probe should be launched with a velocity of 10 AU per year. Then increase the speed to 20 AU per year for the 500 AU mission. Advances in propulsion should allow the 1,000 AU probe to achieve 40-50 AU a year, and have the 10,000 AU probe cruise at 200 AU a year.
More info on interstellar precursor missions.
100-400 AU http://interstellar.jpl.nasa.gov/interstellar/ISP_Space2K_v4.pdf
10,000 AU http://www.engr.psu.edu/antimatter/Papers/AIMStar_99.pdf