This is a more unusual mod, but it’s one that caught our eye: Sonic 3 in 16:9 widescreen, by Eukaryot (@Eukaryot3K), who just announced the release via Twitter.

Interested in giving it a whirl? You’ll need the Steam version of Sonic 3 & Knuckles installed (hence the unusual part!), which Sonic 3 A.I.R. is built upon.
Download via Google Drive (recommended): http://sonic3air.org/downloadgame2.php
Alternative direct download: http://sonic3air.org/downloadgame.php