My Brother, My Brother And Me - 3 brothers giving not-so-serious advice to listeners, reacting to questions from Yahoo Answers (when that was a thing), and later adding other segments, and overall being funny/silly (note: sometimes they make references that go over my head, but they’re still enjoyable. These references might be best enjoyed by midwestern Americans who grew up in the late 80’s/early 90’s)
My Dad Wrote A Porno - 3 people reacting to an “erotica” book series that one of the guys’ dad published (I would say the books are maybe only 5%-20% explicit, depending on the chapter) (some of the characters’ voices can be annoying/grating, and the narrator tends to repeat sentences after they react to them which can be annoying as well)
No Such Thing As A Fish - the behind-the-scenes staff of the show QI bring up interesting facts and tidbits from history/nature/etc. (each episode is split into 4 parts where each member brings up a fact and the others react to it and bring up related facts)
If I Were You - Jake & Amir from CollegeHumor giving advice to listeners (mostly in a sarcastic/tongue-in-cheek way but sometimes genuinely), mostly about relationships/dating
SmartLess - Jason Bateman and Will Arnett (Arrested Development) and Sean Hayes (Will & Grace) interview a famous person each episode where only one of the hosts known who it is beforehand (it gets better after the first few episodes, though some conversations are less funny/entertaining than others)
Conan O’Brien Needs A Friend - Conan interviews a famous person each episode (I like the interview part better than the introduction, and similarly to Smartless some conversations are less funny than others)
If you watched The Office (US) - Office Ladies - Jenna and Angela from the show reacting to each episode of the show and bringing up behind-the-scenes stuff (some of episodes include interviews with other cast members/staff) (might not be as humorous as the others but still fun to listen to)
On the humorous side: