1. If they have a large readership, advertising via Google.
2. If you have even some traffic, you could make money on the blog with referral links like Mommy bloggers who get a cut of any sales of items that are sold through the link on their site.
3. Paid reviews are an option, but the FTC requires you to say that's the case.
4. If you have written books, you can use the blog to essentially promote the book and your personal brand.
5. If you sell a product or service, the blog can be a constant promotion for that product or service, a funnel to capture traffic of interested people.