Companies are always looking to run surveys and polls. If you have an active and engaging community, you can accept payment from companies and run polls/surveys to your community on their behalf.

Advantages: If you have a big mailing list, social following and readership, then you can charge a premium to companies that are looking for data.

Good quality data is a hard thing to come by and it's often what a lot of businesses are after, so there's a lot of money to be made in doing this.

Alongside this, there's loads of software that you can use to run the polls/surveys which means you don't need to get your hands dirty with code.

Disadvantages: If a business is going to pay a significant amount of money to run a poll/survey on your blog, they will often want as much information as possible about your readers.

This will often require you to invest in software to get more insights into your website visitors/social media following/email subscribers. In addition to this, you need to ensure that you get a good response for the poll, so blogs with a small readership can't really go along with this option unless they're in a very tight niche.