As Daniel nicely outlined below, the US astronomical community is currently going through its decadal exercise in naval navel gazing. The decadal review process assesses the state of the field, figures out where best to invest limited resources to maximize the scientific return, and creates a report that lays out the scientific and technical priorities for the coming decade. This document becomes close to holy writ for funding agencies, who use it as a roadmap for deciding which facilities deserve funding. The decadal reports for astronomy have served us well in political circles, since they offer clear prioritization based on community-wide input, rather that a long list of projects clamoring for support. (The rumor is that other scientific fields don't do quite so well at prioritization during similar exercises, perhaps because they lack astronomers' long reliance on shared facilities, which forces us to practice playing well with others on a regular basis). Right now the review process is evaluating key areas where we think substantial scientific progress can be made in the next 10 years, either with existing facilities, or with new ones. We've also been tasked with identifying areas with unusual "discovery potential". This work is being done by various "Science Frontiers Panels", after community input in the form of white papers (see the list here) and town hall meetings. Our reports then go to the "Program Prioritization Panels", who then start the hard work of ranking the various missions, facilities, and projects, in light of the priorities identified by the SFP and the "Infrastructure and State of the Profession Study Groups". (Horrific org chart can be found here.) So, given that the SFP's are encouraged to gather input from the community, I am throwing open to the floor to your thoughts on the important scientific opportunities in astronomy and astrophysics during the next 10 years. I'll do my best to get the info to the relevant committees, particularly if you tag your suggestions with your preferred subcommittee:

Planetary Systems and Star Formation

Stars and Stellar Evolution

The Galactic Neighborhood

Galaxies Through Cosmic Time

Cosmology and Fundamental Physics

It would also be helpful to let us know whether you're a professional astronomer, physicist, or interested bystander. Please use pseudonyms if you'd like to be anonymous, so that we can follow the thread of discussion more easily. There's also a nice Facebook discussion group hashing things out here. Feel free to join in either venue.