Now you can easily +1'd your favorite site, even if the websites doesn't has a Google +1 button added.
+1's can help your friends, contacts, and others on the web find the best stuff when they search. If you use Chrome, you can install an extension that lets you +1 any Web page. By installing the +1 extension, you can publicly +1 any page that you're visiting with one easy click.
The extension is developed by Google and it acts just like a +1 button: it shows the number of +1's and it becomes blue if you've already +1'd a page.
You can manage your +1's in a new tab on your Google profile. You can show your +1's tab to the world, or keep it private and just use it to personally manage the ever-expanding record of things you love around the web.
An obvious privacy trade-off is that the extension sends the list of the pages you visit to Google's servers, but this information is not associated with your account. "Google doesn't keep a persistent record of your browsing history as part of the process of showing you a +1 button or otherwise use the fact that you personally have visited a page with the +1 button. Google may keep some information about your visit, usually for about two weeks, to maintain and debug its systems," explains Google.
You can download the extension from the Chrome Web Store here.