I heard this one on television awhile back:
“This is you know who. I’m not you know where; so leave a meassage after the you know what (BEEP).”
[Kevin McDonald] “We’re not here. We’re… somewhere else…” [/Kevin McDonald]
My dad’s colleague’s outgoing (ha!) message goes like this:
“You know what to do.”
It was his business number’s answering machine. His wife made him change it.
Record the opening line to Pink Floyd’s * Comfortably Numb *.
Hello, is there anybody in there? Just nod if you can hear me. Is there anyone home?
Another one I heard recently, which was short and sweet.
You’ve got my machine.
You know the routine. BEEP!
Only family and telemarketers call me. The family loved it. 
If you’ve nothing better todo for a few days, plenty of suggestions here
My favourite (only managed a few pages in mind)
Hi! John’s answering machine is broken. This is his refrigerator. Please speak very slowly, and I’ll stick your message to myself with one of these magnets.
I keep putting a message on our voice mail, and mom keeps changing it back to the generic “Hi you’ve reached the – residence, we can’t come to the phone right now but if you’d like to leave your name number and a short message we’ll get back to you as soon as possible.” I HATE that. It’s the vanilla of answering machine messages. Every time I get our voice mail I put in the commands and change it to
Hi. You’ve reached the — residence. If you’d like to leave a message, talk when it beeps. If you’d like to leave a fax, buy me a fax machine. [beep]
“Please hold. BEEP.”
Of course, I’ve never had the guts to try it myself…
Mine used to go as follows:
“Hi. David’s not here right now, so go ahead and leave a – oh, wait, hold on a second, I think I hear myself coming in the door right now. (pause) No, guess that wasn’t me. So just go ahead and leave a message.”
I actually had people earnestly leave messages saying, “Hello? Hello? Are you there?”, as if my machine really could hear me coming.
I loved the Folgers Crystals suggestion! I’m going to record that one right now!
– Dave
My current message:
Hi this is (Tiglon1) thanks for calling. You know what to do and when to do it. Bye.
I always wanted to do the Rent thing and say “Speak!” But I HATE it when I call a machine and it doesn’t tell me the first name of who I am calling. Mine at the moment says “Hi, it’s Swiddle’s machine. I screen calls, so if you hang up without leaving a message, I’ll find you and kill you. If you’re a telemarketer, I don’t have any money, so I can’t buy whatever you’re selling. ciao.”
Here’s one I had a while back, but it was kinda long so I changed it:
"You’ve reached (Crundhy Frog)'s answering machine. If you’re calling to sell me something, I don’t have the spare money. If this is a bill collector, I’ve already sent the money. If this is Dave, you owe me money. If this is Mom or Dad, please send me some money. If this is a good-looking single woman, don’t worry: I have plenty of money.
My grandparents says
(grandpa)“Okay talk now”
(grandma)" Now?"
(grandpa) “Yes, now, the little light is off.”
(grandma) "Into that little square)
(grandpa)“Hurry up, yes there.”
(grandma) “Okay… (much louder) Hi, you have reached… Please leave a message. What that okay?”
(grandpa) “That was fine.”
(grandma “Did you let go of the button?”
(grandpa) "Of course I did. I’m not an idio…
beep
Of course, they didn’t do that on purpose, they just really don’t know how to work their machine.
An ex-boyfriend had the following message for a while. He had two kids that were away at college:
“Hi, you have reached . . . If this is Kim and you need money, please press one; if this is Dustin and you need money, please press two; if this is a bill collector and you need money, please press your face into a wall.”