The Yellowstone has been giving up some great trout lately. The streamer fishing has been producing some real trophies here lately.
The lower Madison was muddy as the lake turned over but has gotten a lot clearer in the past few days. Baetis are coming off in the afternoons and you will find many fish in the 10-16 inch range rising to these small mayflies.
In my opinion the fishing doesn't get much better then it is right now on the Missouri river. You can pick which technique you want to fish and have success at all of them.
The Gallatin and East Gallatin are fishing great right now. Overcast days have been the key for great dry fly fishing. The mayflies have been coming off after 1pm.