Hmm. Well, I can say there are a lot of them, and the number is probably even higher since I have lots of followers, but let me put together a sample list:

Some are obvious. Pornographic sites. Any links to The Oatmeal or similar. Sites that use links to other, similar sites to harvest cookies (this is a popular thing on social media sites where people share links to their own side blogs). Sites with large amounts of text-heavy, slow-loading content and no apparent purpose. Sites with a lot of flashing lights. Some that I've seen in news articles:

Toby Fox's video game "Undertale" gets malware

Toby Fox's video game "Undertale" goes on sale at Steam

Some game you've probably never heard of becomes a hot social media meme

A popular social media site, Facebook, sells user data to a Chinese company, which sells it to a data analysis company, which sells it to advertising firms

Some are obviously bad, but the reason for them is that they're just doing the same stuff everybody else does:

A political candidate uses his own blog to spread links to his campaign website (the website may or may not contain malware)

A political candidate uses his personal website to spread links to his campaign website

A political candidate uses a personal website to "review" a video game released by another candidate

A political candidate pays for a Facebook ad to link to his campaign site