Getting a survey of customer interest without giving too much away?
sharpn: Ok, the chance your idea is stolen is not zero - but it's a lot lower than you think.
That said, there are a few things you can do without revealing your idea; use google trends to identify search volume for the problem you're solving, search forums for questions indicating frustration at the lack of your solution etc.Mechanical Turk can also generate cheap data about the likely size of your market & whether your solution is viable. There was a post here yesterday with good advice on how to screen for quality there.
[edit] http://www.itworld.com/internet/76659/experimenting-mechanic...I've also seen a friend garner some useful data with a small adwords campaign testing to see if people would click on 'solve problem x' ads - but that's a dubious tactic if you don't have a product yet...Good luck.