What is my audience interested in?
What is your target audience? What industry are you in?
Is it marketing? Is it toys? Is it furniture? Is it finance?
Search for the top 5 blogs in your industry. Take a look at them. What are the headlines on the site? What offers do they have in exchange for an email address?
They wouldn’t be offering it if they didn’t think people were interested. And the fact that they’re in the top 5 probably means that people are interested.
Take action: Do the research - find the blogs, look at their headlines, figure out what your audience is interested in