Crazy-ass circus-themed music, eh? Ok. Initially, I was going to post Panic! at the Disco's "I Write Sins Not Tragedies", but I feared @Dalans' wrath, so I'll leave that one to you to look-up. P!atD is heavily influenced by the whole creepy-ass circus thing; you get a lot of those undertones in many of their tracks.
Now, as for stuff more applicable to this group, might I suggest Chris Vrenna's deeply disturbing soundtrack to American McGee's Alice?
There is also the dark humor of Steven Page, now ex-Barenaked Lady. Here's his circus-themed delightful song of a person dying in a horrific car crash.
I'd also recommend the entire soundtrack from Amelie, simply because it's an awesome movie, and although isn't exactly circus music, definitely strikes a similar chord in that genre. Plus we don't get nearly enough accordion in our lives: