The Lower Madison is a great option right now. Water temps in the low 40's, flows around 1250 cfs, and clarity is good. Flows have been steady for a few days now which is always a good thing. A double nymph rig with a worm, egg, sowbug, midge, or perdigon is your best bet. Keep your eye out for risers eating midges in the soft water and along the banks. Streamer fishing will continue to improve as water warms.
Dries:
parachute adams, griffiths gnat, buzzball, Z-lon midge
Nymphs:
Zirdle Bugs, zebra midge, perdigons, tung dart, egg
Streamers:
Sparkle minnows, Kreelex minnows, wooly bugger, sculpzilla