That was the question I asked myself when I saw the +1 button being presented, but realized that they had not launched it yet. But there is a way to test it right now, and go plussing up your sites (and my of course) in the search results! You can sign up for testing at google.com/experimental, the only thing you need is a Google profile.
Update! It is now possible to add the plus one button to websites!
Testing the Google +1 button
On the page google.com/experimental there are a several things you can test, it is the plus one button, the Google search engine results keyboard shortcuts, and something called accessible view. Just click “join this experiment” and you are in. Then you can go to Google.com and search for something. For example “Google adds plus one button“. If you are logged in to your Google account, you will now see the Google plus one button on the right side of the title on each search result.
Test to click plus one on something, and you will see this popup:
Now, go out and “plus one” all of your own sites and all the sites you like! Test the Google plus one button to its limits! Then we just have to wait until Google rolls out this function for everyone, so that we can start using it for real, and maybe see some SEO benefits from it!