Since the recent addition of new communities for Unix and Ubuntu within the StackExchange (particularly ServerFault), I propose that tags posted to SF with relevant tags ("Ubuntu", "Solaris", "Unix", etc.) be automatically cross-posted (or linked) to those communities.
I think that this would allow those who wish to focus on their chosen area of interest to only look in those communities , but maximize coverage for Question Askers ("Questioners"? "Queryphiles"? "Inquisitors"?), such that they would only need to post to SF, but those relevant tagged questions would filter down to the sub-communities.
(And answer questions such as this.)