This site wants to be placed on your bookmark bar asap. Multiple times when dealing with badscience and the like you'll get the authors quickly removing the incriminating evidence. MyLifeMyID being a good example.
Normally you'll have to download a copy of the page and then re-host it yourself (opening yourself up to copyright infringement claims) But BackupURL seems to cut out the middleman. Simply paste your chosen URL in and it will spit out the address of a newly made cached version that will be immune to any Orwellian tampering.
I've just this minute stumbled across the site so I've no idea about their reliability in the long term, but as an additional tool to your activism it can hardly hurt. I would still do the old print-screen and webpage saving just to be sure though.
Forgive me if this is old news to some, but I've only just heard about it.