Obviously not every site is archived, but it's a pretty neat tool to see the how the web has evolved over the years, or how sites like Google looked when they first started.
Also, most links on the pages were also archived, meaning that you can get news articles on bbc.co.uk from 1998.
Some of the caches may display strangely and thin though, which is probably because sites back then were created for a certain audience, such as users with 640x480 resolutions which may seem extremely small these days, but was quite common back then.
when I searched on pre-historic google (lol) i got this code--
<a class="postlink" href="http://pastie.org/1387655">http://pastie.org/1387655</a>
(it's to long and I don't want to spam the page so I used pastie...)