Apple has removed all download links for the Messages beta OS X app from its website. Messages was released as a public beta last February for all Lion users to try. It looks like Apple has done all the testing it needs, as the beta page has now been removed from the Apple site and visiting the page from a search engine will forward you to the OS X portal.
That's probably the last we'll see of Messages until it ships as an included app in OS X Mountain Lion next month. If you're a Lion user that's not looking to upgrade anytime soon, don't despair: the Messages beta still works if you've already got it installed on your Mac, and the direct download link still works — for now — if you don't. It's likely that the Messages app will appear as a download from the Mac App Store soon — Apple had a free public beta of FaceTime prior to its inclusion in OS X Lion that later went on sale for $0.99.