serious substantive questions
Various ask-style subreddits have popped up lately:
/r/AskScience
(
2011 best big community
)
/r/AskEngineers
/r/AskHistorians
/r/AskAcademia
/r/Math ⇒ /r/CasualMath ⇒ /r/LearnMath
ask classroom questions
/r/CheatAtMathHomework