Inexpensive ways of mobile app promotion?

So let's say we have a finished free mobile game (namely this one), but don't have either experience or financial resources (especially considering current dollar to ruble exchange rate Grin

) for all those massive promotional operations; still, it would be nice if someone heard about the product, right?
So my question is: what are the reasonable promotion solutions for more humble developers? I've found a couple of neat free services while browsing through this forum, but I am sure that there is a lot more of those; maybe I've just missed a topic which included some sort of a list of those?