is there an App for that?

Where on the web can I best ask the question if there is an App to do a certain thing? That something to be described in plain English. Some forum, perhaps this one? A site also frequented by developers who might answer: "working on that, subscribe to my newsletter to be the first to know when it is out". Or an explanation "forget it, it is not allowed by Apple" is also helpful. A site that also functions as market research, with votes for ideas for Apps. Postings organised with tags.

Just searching with keywords in the App Store does not give me the Apps I am looking for.