From Sterling and Shapiro's "The Art of Prolog" a procedure to concat two difference lists in O(1) time (from memory):

    append_dl(A - B, B - C, A - C).

Prolog. It fits my brain.

I really suspect Prolog would fit my brain, but I have trouble thinking of real-world scenarios where it would be useful to hack in. Other than the tutorials out there that focus on toy problems, what are some other examples of where Prolog is actually a good technology fit for side projects?

Software which includes dependency graphs are a natural fit

Do a google search for: prolog robotics

I recommend The Python Cookbook: http://oreilly.com/catalog/9780596001674. It's not a reference in the sense that it shows you the language syntax or tells you the details of the standard library, but it shows how experienced Pythonistas do things in a way that might not be obvious to you if you come from a language like C or Java, or until you're Dutch.

"2001: A Space Odyssey" - Stanley Kubrick

"Eat Drink Man Woman" - Ang Lee

"The Ice Storm" - Ang Lee

"Wonder Boys" - Curtis Hanson

"The Apartment" - Billy Wilder

An engineer, a physicist and a mathematician want to catch a lion. The engineer goes to Africa, builds a cage and traps the lion in it. The physicist builds a fence around Africa and pronounces: "I've trapped the lion". The mathematician builds a cage, climbs inside and pronounces: "I am outside".