Chrome/Firefox/Opera/Safari: Viewing Google's cached pages is nice for when a site goes down or updates, but you can only view a cached version of that one page. This user script will let you browse the cache of the entire site.
Usually, when you visit a cached page from Google, clicking on that page's links will take you to the actual, uncached link. This is pretty much useless, since if the site is down (which is often when Google's cache becomes so useful), it's just going to point you to a dead page. Google Cache Continue Redux adds a yellow "cache" link next to each link on a cached page, which will take you to the cached version of each of those links. Thus, instead of being stuck browsing a dead site (or searching for the exact page you want), you can browse a cached version of an entire web site. I'm surprised this isn't part of Google's system, frankly, but it's a really useful user script for when sites go down and you need to access them.
Google Cache Continue Redux is a user script that works in Chrome, Opera, Firefox with Greasemonkey, or Safari with Greasekit.