Check out iPushIt ...

[Macom2009]

Send images and text for free to other iPhone users with this little app. Nice UI design and very fast. Uses Apples Push Notifications also. See :

iPushIt

 

[kicko]

I am tempted to try this one for .99

I updated my iphone to 3.1 but i did not do my wife's for fear of the issues some people have been having. This would be great for text/MMS.

 

[macduke]

How can this be?!? The text bubbles are too shiny. Why didn't Apple reject this for confusing me?

 

[parthc007]

I poo S*IT

Lol sorry couldn't resist. On a more serious note, this looks very similar to Ping!