Minisite Education
Teenagers have some problems and opportunities with mini sites which are all their own. On the one hand, they haven't lived long enough to have done much besides go to school. They are probably not experts in any subject area so it is harder for them to think of things to write about.
On the other hand they are probably more comfortable with the technology. Seniors and baby boomers have lots of subjects they know about, but may find it really hard to deal with the technical aspects of mini sites.
It's an obvious place for a joint venture. Talk to a grandparent or old person and ask them to write up everything they know about some subject you find interesting too. They provide the content for the mini site and you get it published, ranked, and earning money.
If a joint venture isn't your style, then write reviews of hot consumer electronics or other things which you know a lot about. Be away these subjects come and go quickly as consumer interest shifts to the latest new thing. Mini sites built on trendy subjects will probably not have a long life. Of course they can make a lot of money while they last too.