I usually avoid adding online secondary sources (most of them are so cursory and unreliable, in my experience) but this one has some substantial information on obscure topics that students often struggle to get information on, such as Bronze Age Mesopotamia. They'll definitely need to be careful with some of the details though and corroborate any information they use.
Another of the excellent sourcebooks run by those Jesuits at Fordham Uni. This is the best online primary source research for the ancient world I've found.
This group is dedicated to Ancient Civs, especially Egypt. I didn't want to just pinch their bookmarks as that's a bit rude (seeings I'm in this group) so I thought bookmarking their bookmarks, which will update, the best way. There are some great sites here.
Although this is an online secondary source site (which in my experience are usually superficial and dodgy) the information seems to be quite thorough and good-quality. That's probably because it's run by University College London. Many interesting and informative themes are picked up. Definitely good for student research or classwork/homework.
I usually don't add secondary sources (I've found books are much more comprehensive - secondary websites seem usually quite simplistic in their treatments) but thought this might be useful for people working with younger classes doing preliminary research or activities on ancient civilisations.