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Of course, borrowing others' ideas is a good way to start, but take good parts from each site, and then come up with your own. And venture out to other non-D&D sites, such as gaming sites, NWN sites, band website, etc.
My Barsoom website is a little less impressive than the ones already listed, but it was very very very fun to create. It's amazing how much you can generate just by doing a little bit at a time.
That's amusing, especially since I'm the co-author of the long dead Karanblade d20 site, lost contact with the primary author, but I submitted a bunch of stuff several years ago that never got put on the site. But do check out the Desert Mage class, that one's by me