Mike, if you think Wikipedia's "interlinks" are impressive, you should check out everything2.com. It was created, and is now run, by some of the same people who started slashdot. It's a Wikipedia-like collection of articles spanning all manner of technical, academic, pop-culture, and personal topics, connected by a powerful database system meant to simulate the workings of the human mind. By aggregating traffic statistics of ordinary users, the e2 engine determines relationships between articles and displays links at the end of each article to topics it thinks are related. This allows for a wonderful stream-of-consciousness-style browsing that can last for hours on end.

As for Wikipedia, though I check e2 first when I want technical information, I'm surprised it only came on your radar recently, Rands. It was a useful and intriguing project even in its infancy, and has developed into a truly incredible resource in the last year or so.