Broadway for Young (and Broke) Adults

Roundabout has HipTix, MTC has 30-under-30, and as you mentioned, Lincoln Center has LincTix. As far I know, those are the only ticket policies on Broadway that allow you to buy tickets in that price range ahead of time. But then you have day-of rush policies for most other shows.

http://www.playbill.com/article/broadway-rush-lottery-and-standing-room-only-policies-com-116003

A few shows sell balcony seats for really low prices (In my experience, it's usually shows from England, because producers there understand the importance of providing cheap options). Right now I know The Play That Goes wrong offers the balcony for $30. Farinelli and the King (also from the UK) will be doing that as well this fall. I'm not sure if there are others.

Clickable:

http://www.broadwayforbrokepeople.com