> You could have an open replacement for e.g. the 555

There is already a kit [1] for a 555-like circuit (I think Dave [2] says there's some reason it can't be used in place of an actual 555) made of discrete components.

But there's no indication that it's Open Hardware, though. :-(

[1] http://shop.evilmadscientist.com/productsmenu/tinykitlist/65... [2] https://www.youtube.com/watch?v=U6qZPx4uD0g