Popup Messages for Mac

Hi there guys!

I was just wondering if there was a way, or even an application that would enable me to send popup messages to other local Mac users (users that are using the same mac as me.) You know, as a sort of way to get information or updates across to them without the use of E-Mail accounts.

Also, if there is such thing, does anyone know of an application that works like an email application so that people can send them messages without the use of internet. Like an email application that only exists for people to send you messages if they are on your local network or using the same Mac as you?

By the way, I'm using Mac OS X Leopard 10.5


Anyone know of anything?

Cheers guys!
Any help greatly appreciated!

I too would be interested in any answers to this question!

Probably not what you're looking for but you could use iChat with Bonjour.
Both are built-in and can be used over LAN. Don't know about people on the same computer.

Yes, but both of them are Instant Messaging services. I was thinking something more like an offline service, like you can do on Windows. So that the Popup message would stay there until that person logs into their account, and not be instant. That's what I mean.

Would anybody else be able to help me?
Thanks.