This reminds me of a browser extension I'd like to see. It could watch over your browsing and construct a graph of the sites you've visited, then allow you to spatially navigate your navigations. Throw in some auto-categorization and you have a nicely organized breadcrumb trail that you can then use to explore new spaces & fill in gaps in your knowledge.
^This! When I'm jumping into a new area, I go through the basics, and then it starts to get hard to see what I've already covered. Something that would make it easier to see that I've missed a section due to the "Squirrel" effect, or just the density of what I have seen, would be a major help.
