You can go to the NASA Homepage and click their icons for 'Space Science' and 'Human Space Flight' which will take you to pages for all the approved manned and unmanned programs currently on the schedule for the next 10 years or so. As for the far future, there are miscellaneous 'studies' scattered among the NASA centers for colonization of the Moon and Mars, but your best shot is to begin with the NASA home page, and from there visit the home pages of the affiliated NASA centers such as Marshall, Ames, JPL which have many excellent documents on a variety of topics. Marshall Space Flight Center, in particular, hosts a number of education pages and you might find something there.