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Zeal seems to date from about spring 2000. A trawl of Google groups indicates that originally editors could earn charitable donations by editing, sounds like a good dot.com plan! Taken over by Looksmart in 2001. GoGuides and JoeAnt are quite new too.
Google Groups is great for finding timelines like that. It'll allow you to find approximate launch dates and people involved.
I don't know of a historical site that has all that info though.
Here is the history of some:
If you need the history of GG.Org let me know what you'd like and I can arrange that. ;-)