Most of these (e.g. Twitter, Flickr) are inaccurate since they're simply using the Wayback Machine which often misses css and images, completely changing the appearance.
Wikipedia strongly reminded me of WikiWikiWeb, http://c2.com/cgi/wiki?WelcomeVisitors. I actually kind of prefer this sparser look, at least for things that don't have a strong visual aspect.
Aside from the inspiration via how quickly knocked together some of these look, it's interesting to see early directions that have since been abandoned, eg: YouTube's dating site style "I am a $gender looking for $gender" drop-down.
They have (http://www.telco2.net/blog/images/amazon%20early%20screen%20...) but once they found something that worked well it makes sense they'd stick with it. A pretty design that causes a 1% drop in sales would be pretty stupid, and I'm sure they've A/B tested such things.
http://www.telegraph.co.uk/technology/6125914/How-20-popular...