If you've got a really active community within your blog that are looking to learn more about what you're writing about, then there could be an opportunity to create a paid membership area.

This would require members to pay a fee to see extra content on your site (usually learning resources). An example of a blog that does this is the Treehouse Blog.

Advantages: When implemented correctly, paid membership areas can become very valuable. Not only are you able to make money from the membership fees but you will also have endless up-sell opportunities.

This could be in the form of affiliate sales, private ad sponsorships, direct product/services sales, plus many more.

Disadvantages: There are quite high barriers to entry for this method. Unless you have a lot of value to add for paid membership, plus a very active and large community, you're not likely to be able to pull it off.

A great article on Pro Blogger goes through some of the top reasons for failure for paid membership schemes, so I'd recommend giving it a read before making a decision.