wheel - 1:26 am on Oct 17, 2011 (gmt 0)
I suspect 1,2 and 6 are already extremely competitive fields full of experts.
3 and 4, yawn.
5 - depends on what you mean by history. Pick a topic, an even, or a person once a week and make them come alive on the web. Seems like opportunity there.
But as a secondary point, you're goal is awfully vague, and doesn't have much point.
You really should have something like 'I am a history freak, how can I build a community'?