Using browser bookmarklets you can fluxgain Like a web page even if there isn't a fluxgain Like button on the page from directly within your browser.
Some other web browser bookmarklet examples for public sharing services include
To set up the bookmarklet in your web browser drag the following link onto your browser "Bookmarks Bar", "Favourites Bar" or "Bookmarks Toolbar". This toolbar / bar may not be displayed by default so you may need go into the web browser menu to turn it on (view it) first.
Update 30/04/13 - based on feedback from the appexchange security review process the bookmarklet now opens a new window instead of using the current window
If your browser does not support dragging links, then manually create a bookmark using the following test as the URL (ensure no spaces are included)
Once you have the bookmarklet in place visit a web page then click on the fluxgain Like bookmarklet to salesforce chatter like it via fluxgain Like.