I don't think there should be a forum for libraries.. it'll be too messy and too unorganised. A dedicated repository or application (which I know has been worked on in the past, don't know if it is still under development) would fit that need so many times better.
As for more forums, even though I support the notion of a generic system design forum.. there are too many as it is, it'd be better to clean up what is present right now and cut the number down to a third or fourth, then we can have a look at what is missing =\ (my point of view).
Besides, at the moment there are at least half a dozen forums that encompass a part of the system design topic..