Proper Motions as an Underutilized Tool for Estimating Distances and   Ages for Nearby, Young Stars
  The recent availability of accurate proper motion catalogs for millions of stars on the sky (e.g. Tycho-2, UCAC) can benefit projects for which age estimates are needed for stars that are plausibly young (<100 Myr-old) and within a few hundred pc of the Sun. Here I summarize how accurate proper motions have been useful in (1) identifying new, nearby, post-T Tauri star populations, and (2) estimating distances to young field stars which are lacking trigonometric parallax measurements. The later enables the calculation of stellar luminosities and isochronal ages -- two quantities critical for investigations of the evolution of star/planet/disk systems. 
Eric E. Mamajek (Harvard-Smithsonian Center for Astrophysics)