Since we're sharing favorite channels, I guess some of us XM guys should share, too.
20 (Top 20 on 20), 26 (Flight 26), 29 (U-Pop), 30 (XM Hitlist), and 60 (Soul Street) I only listen to once in a while if I notice something good is on as I scroll through the list.
40 (Deep Tracks), 41 (Boneyard), 42 (XM Liquid Metal), 46 (Top Tracks), 48 (Squizz), and 49 (Big Tracks) are the main ones I listen to. It's nice that they're all together so you can scroll through them pretty quickly. I probably listen to 49 more than anything.
150 (XM Comedy) is pretty good when I don't really feel like listening to music or I'm in a bad mood. Pretty good programming - Lewis Black, George Carlin, etc. 151 (Laugh USA) has never really done it for me.