I'll second Ronsonic.
Running is boring and no fun. If i'm going to be out "exercising" i'd just as soon be doing something that i love-- namely cycling.
That said, when it gets all gloomy out and cyclocross season is upon us, i set up my practice barriers and run and ride around the block for about 30-40 mins. Half the roads around my neighborhood are dirt/gravel and i get almost as dirty and muddy as i do in a race!