If you'd like to learn some slide try the Stephan Grossman video (Stefan Grossman's Guitar Workshop) it's a good one. Bob Brozman also (Homespun Tapes). Slide doesn't have to be played on a resonator guitar but man it sure helps, regular acoustics just don't have the volume and sustain. Also take a look at Brad's Page of Steel and Planet Dobro to wet yer whistle for slide guitar.