I reckon a simple list of things that people want, that others can vote on, so that then a wandering bored developer can go and take a look and see what to hack on (and something that's interesting *and* wanted by other people is the sort of thing they will want to do).

When I say list, the onus should be on the requester to make sure there is sufficient information about the app, screenshots, links to source etc., as there's nothing worse than someone asking for an app to be ported and just giving a name which returns lots of unrelated hits on Google.