I'd love to play with the Ohloh API to retrieve stats on collections (users, projects) but unfortunately the kind of functionality that I'd need is not implemented in the API yet.
Correct me if I'm wrong: currently the only fields that can be used on a query are "name" for accounts and "name or tags or desc" for projects. This dramatically limits what can be done with the API.
Ideally I would like to be able to run complex boolean queries based on any combination of account/project properties, or at least on those properties for which the API already supports sorting.
Moreover, both for projects and users, it would be very useful to have the primary language represented at collection level so as to be able to query the API for, say, Ruby projects or developers with Ruby as primary tracked language.
Advanced query support would make it possible to access the Ohloh DB in a variety of useful ways and allow developers to write new applications on top of the API. Imagine, for example, an application retrieving a list of developers who write in the same languages in which I write code and located in my neighbourhood. There's a lot of fantastic applications that could be built if Ohloh made a further effort in exposing its data.