I guess what people can participate in, will vary according to skill set/interests etc, such is the nature of open source development... you can't say do X, only suggest A/B/C are important.
I guess issue tracker is best place, but its got some serious limitations (e.g. no priorities, and only @johannes can tag etc)
if we have a few developers then perhaps a 'development' category here, to discuss such things. its pretty important, we all head in the same direction, and also don't tread on each others toes... and that is easier said than done, and gets more difficult once you have more people involved.
@johannes what thought have you on 'managing' this?
EDIT: ok, created as a new topic, as perhaps we need to discuss the 'how' to do this a bit.