My solution to this problem was to purchase "150 Fun Songs for Kids" from the iTunes store.

"This is going to be amazing," I thought to myself. "That's like, half a year worth of songs!" I was convinced that this would be the best ten dollars I ever spent, and I'd be lying if I didn't tell you that the music collection paid for itself the moment Isaac heard "The Ants Go Marching..." However, the part of me that still laughs whenever I hear someone talk about Uranus got a kick out of some of the song selections.
The best of the best:
This Is the Way the Ladies Ride
Six in a Bed
Let's Play Dressup
Cockles and Mussels
Rub-a-Dub Dub, Three Men in a Tub
Ride a Cock-Horse to Banbury Cross
Weenie Man
I'm not exactly sure what some of the messages these songs are sending. Justin and I, forever trapped in our 13-year old minds, analyze the songs.
"Why doesn't old Mother Hubbard have any food? She can't even feed her poor dog."
"Jack's mom was lazy and sent him up a hill to get water and he busts his head open?"
"The bridge in London is falling down? Why wasn't it shut down by some bridge inspector?"
"Who would put a cradle up in a tree, knowing that when the wind blows the baby is going to come crashing down? Who thought that was a good idea?"
Thankfully, I don't take any issue with Isaac's favorite song about the ants. We now sing that like it's UT's fight song.

