I'm not sure if such a resource exists but if it does this is surely the place to find it...
I listen to That Mitchell and Webb Sound an awful lot and I'd love to know who wrote certain sketches. They've got a rather large pool of writers so it's hard to pinpoint who wrote what from episode to episode, does anyone know if there's a breakdown of each episode with sketches attributed to their writers?
Every now and again Hazeley/Morris will mention a Michell & Webb sketch they wrote on their Rule of Three podcast and I've heard John Finnemore reference some of his contributions from time to time but the geek in me wants a comprehensive list!