Each week, in a free podcast that lasts about a half hour, journalist Sarah Koenig walks us through the story of Adnan Syed, who was convicted in 2000 of murdering his girlfriend in the Baltimore area. Koenig plays tapes of police interviews; reads from the diary of the girlfriend, Hae Min Lee; and plays back phone calls Koenig received from Syed in prison. Koenig is an outstanding host, making insightful observations on how one piece of evidence can support opposite theories, or how difficult it can be to actually remember what you did on a certain day. Koenig assesses the credibility of those involved, critiques the work of the detectives and points out when she thinks something doesn't add up. But in the end, each listener will have to decide: did he do it? Chat rooms have popped up to debate various theories. Serial is the most popular podcast ever, with 1.5 million people listening to each episode. I'm so hooked, some days I wish my commute was longer.

- TIM COTTER