What are the most unusual channels you have used to attract users?

Quora is sill under used. You can use tool like https://www.qapop.com/ to leverage it.

Reddit Community: Lots of homogenous groups of people with similar interest. Tightly controlled by mods and strict community conditions. FB Groups: Another popular hangout zone for like-minded people. From real estate search in cities to coupon hunters. Much easier to post and grow. Online Forums: Lots of online forums have a similar experience as above and good to reach people. Twitter: Another place to find early adopters and like-minded people. One of the best platforms for early distribution building. Youtube: This is another medium that has a collection of influencers and their cult-like Quora: Another Q/A platform and still very popular space to find out answers to some really interesting questions. Though some are popular, how you go about each one of them can be unique in themselves as well !