Simon F said:
Get some pipe organ recordings.
Ditto to that - pretty scary sometimes. There're also a couple of incredible recordings of the 1812 floating about that have real cannons at the end.
Somebody asked a similar question on another forum and I had a flick through my music collection to pick a few "lowies" out. I have quite a bit of DnB but it hardly ever goes <30Hz; no point muddying up delectable beats with sub-bass that chavs can't even hear on their Kenwood 6x9s.
For a bass "workout" on the other hand, you can't beat the likes of Dillinja etc. I don't own much Electronica, but I'd guess that's where the real low stuff can be found (i.e. sub bass just for the sake of it).
2:30 into The Prodigy's "Charly (Trip Into D&B version)":
Avril Lavigne, Sk8er Boi 1:50. Not too shabby...
Intro to "Poor Leno" by Royksopp:
Blackalicious - "It's Going Down (Bink! Remix)". This is jazz hip hop with some serious bass:
0:18 into "Lullaby" by A Perfect Circle. This was the most violently bassy track I could find:
There's sustained output below 10Hz. It should come with some kind of warning!
J-Lo's "Jenny From The Block" goes quite low too (frequently below 25Hz, AFAICT). Don't have a recording of it though... sadly.