Google+ and +1 Buttons
I recently joined Google+, and so far I like it. It's a really nice mix of my favorite Facebook feature and my favorite Twitter features. Unlike these features, Google+ allows you to concentrate your posts into specific groups, or circles. I also like how well the mobile app works compared to the Facebook and Twitter apps. This is mostly because the service was created with mobile in mind. At some point I want to try the "Hangout" video chat feature, as well as the "Huddle" mobile chat feature. Since this is still in Trial Beta, however, there are still a few problems, for example showing only first names in the chat, and not showing information when hovering of the name like with GTalk. Like I said, it's still in Limited Trial Beta, so that's where the feedback from comes in handy, and hopefully the fix with when they can.
A nice feature of Google+ is the +1 button, their version of the "Like" button. A unique feature of the "Like" button is its ability to influence search results. Even though Google+ is still in beta, web developers can add the button to their sites though a fancy plugin. Just include the script tag and place the "plusone" tag where you want it. You can find the code and custom options in Google's Webmaster page.
As you can see, I've already added this feature to my site. Feel free to give me a +1, and while you're at it, like and tweet me as well.