OK, I'm trying to post this again.
The Gizmo's Freeware site has a page full of
Free Computer & Internet Books Online. They're my favorite site for freeware because of the reviews, comments from users, guidelines about what programs can be listed, etc.
They list 119 sites, and users have mentioned more in the comments. Not everything is going to be up your alley. (They list Memoware, which does use mostly Palm formats. But a program like Calibre should be able to convert them into a format you like as they are DRM-free.
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