Here are a few post ideas for your stock market blog:
1. A Beginner's guide to stock market investing.
Recommended Read: A Blueprint To Making Money Online.
3. Interpretations of stock market terms.
4. Guides on how to understand and interpret financial statements.
5. Long term strategies to investment.
6. Extensive coverage of fundamental and technical analysis.
7. "How to" posts [Eg: How to pick up fundamentally strong companies for investing?]
8. Comparison of brokerages.
9. Corporate actions and how they impact the stock prices.
10. Your very own Multibagger ideas. Be careful as to include a detailed analysis on why a particular stock makes it to your list.
11. Top performing stocks over the years.
12. Guides to Mutual fund investing (including comparison of various mutual fund products).
13. Coverage of events likely to impact the market.
14. Risk and how to manage it.
15. Portfolio management tips.
16. Guides to trading in the Derivatives segment.
You could also create video tutorials and posts and announce your own stock market trading classes through your blog.