The only shows that if one's on I really get excited about are Top Gear, the Daily Show, MPFC, South Park and the Colbert Report...
'How it's Made' gets honorable mention, because it's made in Canada, has awesome *cough* background music, and is so boring but strangely fascinating.
Sometimes Antique Roadshow UK is on BBC America when I get home from school and for whatever reason I could probably sit and watch that for hours...