Depends on what you like.
For Jazz and Blues:
1. WBGO (128 kbps): shows I like include Blues Break (weekdays 2:00 to 4:00 pm (all times Eastern)); Portraits in Blue (Friday 8:00 to 9:00 pm); Saturday Morning Function (8:00 to 10:00 am); Rhythm Revue (Saturday 10:00 am to 2:00 pm)
2. WESM (128 kbps): Blues Train (Saturday 3:00 to 5:00 pm); Beale Street (Saturday 6:00 to 7:00 pm); Red Rooster Blues (Saturday 7:00 to 8:00 pm); American Routes (Saturday 8:00 to 10:00 pm)
3. WGMC (128 kbps): Big Road Blues (Sunday 5:00 pm); Blues Spectrum (Sunday 7:00 pm)
4. KCSM (96 kbps): Jazz in the Afternoon (weekdays 5:00 to 8:00 pm); American Jazz Countdown (Sunday 3:00 to 5:00 pm)
Contemporary (pop, rock, etc.)
1. KPTZ (128 kbps): Music to My Ears (Wednesday 7:00 to 8:00 pm); American Routes (Saturday 5:00 to 7:00 pm)
2. KRCL (128 kbps): Sagebrush Serenade (Saturday and Sunday 12:00 to 3:00 pm)
3. KZFR (128 kbps): Woody and Friends (Monday 12:00 to 3:00 pm); Playing [Grateful] Dead (Friday 4:00 to 6:00 pm); Devastation Sounds [Reggae] (Friday 6:00 to 9:00); Island Rhythms (Saturday 12:00 to 2:00 pm): 2 Penny Opera (Saturday 2:00 to 4:30 pm)
4. WDRT (128 kbps): Blue Monday (8:00 to 10:00 pm)
5. KUTX (192 kbps): Laurie Gallardo (Monday to Thursday 3:00 to 6:00 pm)
6. KRCW (192 kbps)
Americana/Traditional/Bluegrass
1. WKSU (128 kbps): Folk Alley (Sunday 6:00 to 8:00 pm)
Classical
1. WQXR (128 kbps): Exploring Music (weekdays 11:00 pm to midnight); Reflections from the Keyboard (Wednesday 10:00 to 11:00 pm); Met Opera (1:00 to 3:30 pm Saturday); Where Music Never Sleeps (Saturday 7:00 to 8:00 pm)
WQXR also hosts "Operavore", a 24-hour station devoted to that art form.