Most likely I've posted this before and forgotten, but in case I didn't or if anyone new is interested...
I first read the Def Leppard Hysterical document a few years ago, and me and my sister spend hours laughing our heads off (almost literally) at some of the misheard lyrics there. Some of my favourites:
Song: Fractured Love
Actual: "Iron fist in a velvet glove"
Heard: "I pissed in a velvet glove"
Actual: "You've gone straight to my head"
Heard: "Your gum sticks to my hair"
Song: Armageddon It
Actual: "Armageddon it"
Heard: "I'm an idiot"
Actual: "Oh, I get hysterical, hysteria"
Heard: "Oh, I'm a stereo, a stereo"
Actual: "I've got a bottle of pills to give me my thrills"
Heard: "I've got a bottle of pills, won't you give me my clothes?"
You get the idea. If you want to see the rest check out Hysterical, here.
There is also KissThisGuy, with misheard lyrics from just about every artist and band you can think of. Well, maybe not, but still lots. Some of them seem kinda obviously fake though...
The reason for the randomness of this post by the way, is that I just re-found Hysterical, and spend a further half hour giggling at that section, and so felt the need to share. Sorry!
Edit: Yay, found even more! AmIRight.com