With Fasterplan, this is much easier now: I created a so-called Fasterplan billboard (no sign-up was required), in which we placed a poll. Besides polls, things like finding a common date or just leaving a text message can be put to the billboard. The URL of the billboard was sent to everybody else who was supposed to participate. Everybody who has the link to the billboard is free to edit it. He can put his name on the list, leave text messages, put images etc. ... anything that could be useful.
I could imagine Fasterplan to be useful for a bunch of other things. Maybe you have any ideas? Let me know!