Another option is the concierge delivery method. This works for some ideas better than others. Eric Ries (and many others) go into greater details. Basically, you manually deliver the service. So, if you were a grocery delivery service, maybe you would find some potential customers and have them submit a Wufoo form with their grocery order and then you would fulfill it. Skillshare did this (http://www.mikekarnj.com/blog/2011/08/01/how-to-launch-your-...).