Here are some pictures from my trip to Gannett Peak, August 15-20, 2008:
I took the Green River/Tourist Creek/West Couloir route recommended by Jack Bennett. This was my eighth attempt (four from this side, four from the other) and first successful ascent. I spent three days hiking in, one day climbing to the top and back, and two days hiking out.
My impression is that this is the easiest route to Gannett Peak, and that the approach has been getting easier in recent years. There is no trail after the first day, but there are more and more trodden paths here and there, some of which lead to easier routes than you might have found on your own. (Going back multiple times also helps, I suppose.)
I was lucky to have sunny skies for six days in a row. It seems like you spend most of your time walking and climbing over rocks and boulders, and rain makes them slippery and potentially dangerous, especially traveling alone, as I was. Hiking poles are very useful.
Packing light is also important when traveling off-trail. On this trip my pack weighed about 25 pounds. I took an ice axe and crampons, but no other climbing equipment. The short section of class 3 or 4 rock climbing needed to reach the summit ridge is not very difficult. You do need to be very careful, of course, and watch out for the weather.
This was my 49th and probably last high point (no plans to try Denali).