Radio 4 Friday Night Comedy (alternates between the News Quiz and the Now Show)
I tend to go for the sciency stuff:
The Infinite Monkey Cage (light hearted)
In Our Time (learned - pick the topics that interest you)
More or Less (statistics, esp picking apart dubious statistics in the news)
Plenty of other science ones - try an internet search or the BBC website.
I listen to them while gardening and jogging as well as occasionally on long bike rides.
You can also get free 'talking books' from
Librivox - although only for books that are out of copyright, and the quality of the readers can be variable! But you might need to clean a lot of bikes to get through a whole book!