Google Wiki2fb2. It produces a fb2 file, which can be converted to epub with Calibre.
Another way to get epub would be to use Wikipedia's menu on the left -> Print/export -> Create a book. Then you add articles to the book and you can export it to an odt file. Calibre converts from odt to epub. However, as far as I remember, the produced odt does not have images. I am not so sure about it, however. Wiki2fb2 claims that it includes images, but I don't know how it handles tables.
I have also found this website, which claims to do what you want, but I haven't used it:
http://www.ereadups.com/