[az09mugen]

I never tried, but I read/heard FB, Xitter and YT also could help spread the word. But it implies you to be active in the community, by posting updates, fixes, news et al about your game constantly, and keeping people updated.

[j-rom]

Agreed. But this can be tough if you don't already have an existing following. I was thinking of including something like a "Change log" on my site where when I launch a feature, the user gets a pop-up that says something like "Here's all the things that we launched while you were away".