All the sites listed below are ones I have found useful and refer to in my posts.
The Rune-Poems: Icelandic, Norwegian, and Old English
Germanic Mythology (texts)
Sacred Texts (Norse and Celtic)
Deo Mercurio is a site about the Roman god Mercury and his Romano-Celtic cult.
Noemi Beck’s thesis on Celtic goddesses is a good summary of scholarship on Romano-Celtic goddesses.
THEOI.com for Greek mythology
The Greek Mythology Link is focused on myths in art and literature, so it’s heavy on quotes from ancient Greek writers.
Ancient Egypt Online for the Gods and Goddesses
The Ancient Egypt site, the section on Pharaonic Religion