I've been running https://simplescraper.io for a number of years, so not exactly a side project but it started out that way.

If time allowed, I'd focus on the AI photo and video generation. Have seen friends hit $500 relatively quickly by targeting niches.

Sounds like a played out category, but if you look closer it's a bit of a potemkin village - many incumbents are not that good or haven't kept up with the latest models.

Each year it gets more crowded out there, but almost always room for better.