Google +1 has been quietly rolled out over the last few months to Google users - allowing them to "+1" (aka, "Like") pages found in Google search results. Today, +1 has been expanded into a number of other Google services, including the Android Web Market:
Pretty neat, right? ROM Manager likes are already piling up. It's very likely we'll see +1 expanded onto the Android Market app in the future, as Google tries to make +1 a part of everyday life for Google users.
Additionally, YouTube, Blogger, and Product Search all have implemented +1. Google has announced a number of partner sites that will have embedded "+1" buttons for content and products (eg, Best Buy, Reuters), similar to the way other social sharing features are incorporated (like Tweet buttons).