I talk a lot about set theory when explaining things to people. (“Who reads my blog? Imagine the intersection of the set of funk music fans and Microsoft Office geeks.”) So I delight when I see an especially useful Venn diagram. Here’s a few recent hits:

• The Interweb
• Valleywag on Blog Nirvana
• Tacos and Cats
• Puppies and Betsy

And finally…

• Hall and Oates

Mathematics are so useful.