I use a Kirk Tilting Head on my monopod.
http://www.bhphotovideo.com/c/produc...t_Monopod.html
The Kirk head is a Manfrotto Tilt head with the addition of a Kirk Arca Compatible Quick Release. I like the Arca Compatible system since both my tripods are equipped with Arca Compatible releases on their ball heads.
Some photographers say that the Manfrotto/Kirk head is not solid enough for a long lens. However, I have used mine with both my 300mm f/4L IS and 400mm f/5.6L lenses on 30D and 40D cameras with absolutely no problem.
IMO, a ball head is not appropriate for a monopod because of the extra weight. Additionally, if you want to switch from horizontal to vertical camera positions, the camera is hanging cantilevered over to the side when using a ball head if using a non-tripod ring equipped lens. I have Really Right Stuff L brackets on both my 30D and 40D cameras so if I want to use a non-tripod ring equipped camera/lens in the vertical position, the camera is positioned directly over the monopod.