In about two months, the Decadal Survey should release its recommended program of new missions for the coming decade. In the meantime, I've set up a poll (actually three) to get your vote for which missions you think should be selected.
The poll is broken into three parts by mission cost class: Larger flagships (>$2B), smaller flagships (~$1.5B), and New Frontiers (~$1B). You can vote for one each of the first two classes and for two New Frontiers missions. All mission costs were taken from the Decadal Survey mission concept reports. The Survey may decide on a different mix of missions (say, two larger flagships and one New Frontiers), but there's only so much flexibility I can build into a poll.
For inclusiveness, I added a comet sample return mission to the New Frontiers list. No price tag was given in the mission concept study, so I arbitrarily decided to include it in this class. I also listed the three New Frontiers missions currently up for selection. One should be chosen any time now, but the other two still would be fair game to fly later in the decade. I did not list the Mars sample return orbiter and return vehicles, which would fly in the 2020s and should be the subject of the next Decadal Survey.
By the way, this mix (1 larger flagship, 1 smaller flagship, and 2 New Frontiers) is my best guess at the mix the Decadal Survey will decide on with the addition of 2-3 Discovery missions.
The poll will close on March 10. I plan to have completed my summary of the missions before then if you want to hold your vote or change it (I think Blogspot allows vote changes) when you hear about more missions.
The following are links to the mission concept studies or to similar mission proposals I've covered in the past:
Approximately New Frontiers
Lunar Geophysical Network
Trojan Tour and Rendezvous
Lunar Polar Volatiles Explorer
Chiron Orbiter Mission
Saturn Atmospheric Probe
Mars Polar Climate mission concepts
Mars Geophysical Network
Venus lander (SAGE)
Near Earth Asteroid Sample Return (OSIRIS-REx)
Lunar Sample Return (MoonRise)
Smaller Flagship Missions
Venus Intrepid Tessera Lander
Titan Lake Probe
Neptune-Triton-KBO or minimum Neptune orbiter
Venus Climate Orbiter/Balloon/Probe
Larger Flagship Missions
Uranus Orbiter with probe
Venus Mobile Explorer
Mars MAX-C Caching Rover
Jupiter Europa Orbiter
Titan Saturn System Mission