As I prepare to ship v1.1 of <a href="http://sixtoeightapp.com">Six to Eight</a>, I'm curious as to what ideas other people might have for Stack Exchange app marketing. How do we reach Stack Exchange users without either annoying them with spammy messages or spending a fortune (or, indeed, anything beyond time).

Six to Eight has been about as successful as I'd hoped so far. I've shipped around 1000 copies: around 450 on the day it first hit the App Store and Jeff tweeted it, 150 when it came 3rd in the SE API competition, then a steady trickle at about 50 new downloads a week. I'm happy, but I think there're more users out there who might like it.

My only real ideas so far are posting on the meta sites, which I've rejected as being too spam like. I guess I could buy Stack Exchange ad space, but I've got no marketing budget for a free app. I like to encourage users to spread the word, especially to the audience on the new Stack Exchanges, but I don't know how.

How are other developers promoting their work, and what can I do to encourage more adoption?