Are there any apps you can use for iPhone 3G?

I have an iPhone 3G and I was wondering what apps you can still buy with the IOS that it uses. I would like it if the apps would be free though! Any help would be appreciated.

Try doing manual searches recommended by this site,
https://sites.google.com/site/appleclubfhs/support/advice-and-articles/finding-apps-for-older-devices
or an app to find these vintage apps,
https://itunes.apple.com/...?mt=8&uo=4

Any apps that require nothing higher than iOS 4.2.1 should run fine on the iPhone 3G - basically anything that will run on an iPod Touch 2nd Gen.