Neptune (Poseidon) and Mars (Ares)
Ecce 7 - Mythology
By Dr. Melissa Schons Bishop, Lenape High School
Find lots of information under the Homework Help section of Mythman.com.
Olympians -  Good short essays here at Mythography - uses the Greek names.
Neptune and Mars on www.pantheon.org.  Excellent overviews of myth and its purpose in antiquity - very specific in scope and clear.  Also click on the links to the Greek names of these gods.
Olympians -  Clickable image map.
For a more in-depth approach to the gods, try Parada's web page, Bulfinch's or Characters of Greek Mythology - all accessible at the Lenape Latin Mythology page.