Reddit mentions of John Hardy

The first thing that comes to mind is "Dueling Banjos." It's one of those songs that, if you can play it well, you will impress everyone that you play for. Period. Everyone knows it, and everyone loves it.

Beyond that, look at old-timey stuff. Even if songs aren't specifically arranged for guitar/banjo, you can normally combine parts that are out there and make your own versions.

Here's a great example. "John Hardy" is an old bluegrass favorite. In its common form, it sounds like this. Because it's such a staple with bluegrass players, you shouldn't have any trouble at all finding chords, and a lot of solos written out for both banjo and guitar, plus there should be tons of versions out there for you to listen to and get the feel of. Of course, you probably aren't going to want to play it like a bluegrass player, so arrange it yourself and make it sound like you want. You can go here and listen to a preview of Ramblin' Jack Elliot's verson of John Hardy, which happens to feature both guitar and banjo, and is arranged to be more folk. There are enough songs out there like this that you can build a pretty decent little repertoire.

Other Folk/Bluegrass songs I'd recommend arranging: Man of Constant Sorrow, Banks of the Ohio, Freight Train, Nine Pound Hammer...actually, there are a whole lot of them.