Great option south of Madison! If my memory serves me correctly this may be the first off-leash dog park in Dane County. It's not as big as Prairie Moraine, nor as hilly, but it is definitely a great park and has a nice variety of trails that take you through prairie and woods. You know what that means... SHADE!!! (Often in short supply at many of the dog parks).
This park also offers quite a bit of water access with several small beaches along the river. It was busy, but not overly crowded by any means, on the random Sunday we visited. The park is rather long and somewhat narrow but there seem to be about four trails that parallel each other heading north/south -- this is nice because if you're trying to avoid another dog (or they're trying to avoid you), there are options for that. YES, THERE ARE PEOPLE OUT THERE WHO WANT TO AVOID LEO JUMPING ON THEM. There. I said it. GEEZ.
Another nice feature here is that there are other hiking trails just off the same parking lot for dogs on-leash. Finally, I think this is the first dog park we've been to where there is a HUMAN RESTROOM! Indeed. And a covered picnic area. (Not directly in the on-leash area, that would just be asking for trouble).
All in all, another great option about 20 minutes south of Madison - and a lovely drive past Lake Kegonsa to get there!