I think unfortunately here is exactly the wrong place to ask: we're in the center, and close to the pure-tech world. The small business ideas left are, almost by definition, in communities that aren't quite so online and well-connected.
I own a handful of profitable small online businesses and I’m building another in my spare time. You can tell by my user name where a lot of opportunity for small time programmers are (crypto in general really) but HN is ideologically opposed to that industry despite the profit opportunities being massive.
And finally I don’t want to reveal any here because I believe Peter Thiel when he writes that “every business has a secret”. On the surface level they are selling XYZ but the reason they win in a competitive market is only known to those running it.
In the traditional space I had a fairly profitable tool that was for a puzzle-like F2P game (think similar to Words with Friends) that ranked highly on Google. That was ad supported but the hardcore players of the game would use it. I wound up selling it for $5k on an app flipper website when the traffic started to decline as the game got older.