Application marketing ideas

As I hole to vessel v1.1 of Six to Eight, I'm funny arsenic to what ideas different group mightiness person for Stack Exchange app marketing. How do we scope Stack Exchange users without either annoying them pinch spammy messages aliases spending a luck (or, indeed, thing beyond time).

Six to Eight has been astir arsenic successful arsenic I'd hoped truthful far. I've shipped astir 1000 copies: astir 450 connected nan time it first deed nan App Store and Jeff tweeted it, 150 erstwhile it came 3rd successful nan SE API competition, past a dependable trickle astatine astir 50 caller downloads a week. I'm happy, but I deliberation there're much users retired location who mightiness for illustration it.

My only existent ideas truthful acold are posting connected nan meta sites, which I've rejected arsenic being excessively spam like. I conjecture I could bargain Stack Exchange advertisement space, but I've sewage nary trading fund for a free app. I for illustration to promote users to dispersed nan word, particularly to nan assemblage connected nan caller Stack Exchanges, but I don't cognize how.

How are different developers promoting their work, and what tin I do to promote much adoption?