In July and August 2005 I had two conferences in Edinburgh. I had a good time at the conferences, but the best part of the trip was the four days I had off in between. I spent three of these days biking around Edinburgh.
There are many possible day trips around Edinburgh, ranging from short, easy, and level trips on the Union Canal towpath and various old train routes; to much longer trips on towpaths, potentially going all the way to Glasgow; to much hiller trips, including going over the Pentland Hills. I did two very different trips, one mostly on the Union Canal towpath (actually I did two different trips on the towpath as I liked it so much) and one over the Pentland Hills.
Edinburgh is also a wonderful city for bicycling. There are very many bicycling lanes and lots of bicycling paths. I used the bicycle I rented to get around the city and to get from the University of Edinburgh dorms to the conference site.