Denny's got a good list of puns going. A few of my favorites:
1. The roundest knight at King Arthur's round table was Sir Cumference. He acquired his size from too much pi.
2. I thought I saw an eye doctor on an Alaskan island, but it turned out to be an optical Aleutian.
3. She was only a whiskey maker, but he loved her still.
4. A rubber band pistol was confiscated from algebra class because it was a weapon of math disruption.
5. A grenade thrown into a kitchen in France would result in Linoleum Blownapart.
6. A small boy swallowed some coins and was taken to a hospital. When his grandmother telephoned to ask how he was, a nurse said, 'No change yet.'
7. When cannibals ate a missionary, they got a taste of religion.
8. Don't join dangerous cults: Practice safe sects!