One of my favourite so far is:
To the works of the heavenly choir
No mere mortal could ever aspire.
There's just one thing, dear Lord,
That I fear you've ignored:
I think that my tiger's on fire.
If you like this kind of thing Wendy Cope included some cracking examples in Making Cocoa for Kingsley Amis IIRC, such as (from memory):
The wasteland: dry land and dry throats.
Then thunder, a shower of quotes,
From Shakespeare and Dante,
Da Dhammyatta Shanti,
I hope you make sense of the notes.
here's one by me
In autumn the wind's in the west
The poet is feeling depressed
When winter comes, spring
Is the usual next thing
I think I might take off my vest
PS still reading Deathly Hallows.
GORDON BENNETT one of the limericks is a Deathly Hallows spoiler - I closed my eyes after the first line - this confirms my resolve not to look at the Internet until I've finished the damn thing