I've got iTunes 10 installed, and have signed up on Ping. 

My handle is "scriptingnews." You're welcome to follow me. 

To be clear, they didn't give me a choice of name. That's the name I chose when I got my first iPod or whatever got me logged into their store the first time. (I don't remember.) I never would have chosen to be scriptingnews on a social network. Not at all obvious how to change it, if I can.  

Here are their first recommendations. They bear absolutely no resemblance to any music I listen to or people I know. Obviously this is very very early days for Ping. 

One thing I don't like about Ping is that it isn't in my web browser. I keep looking for the Back button. I keep wanting to find a URL so I can publish a link somewhere else. I think this is a big lose. It's the only social network I've ever tried that isn't in the web. Right now I think that's a deal-stopper. 

So I played one of my current favorites thinking there would be an easy gesture in the iTunes interface to tell my Ping followers that I like it. After all why bother integrating it with iTunes if there is no integration? Well, there's nothing in the right-click menu for pinging the song. No menus, nothing anywhere in the user interface. What the heck were they thinking?? Hello, anyone home at Apple?? 

Conclusion: There's nothing, at this time, to do in Ping.