Saw this mentioned on the Classicists list; looks useful (although each section of the alphabet is a pdf):
A Dictionary of Classical Mythology
quidquid bene dictum est ab ullo, meum est
quidquid bene dictum est ab ullo, meum est
Saw this mentioned on the Classicists list; looks useful (although each section of the alphabet is a pdf):
rogueclassicism 
useful as long as you don’t want to research Athena! ‘Athena (Ἀθηνᾶ). This article is under revision. See instead “Athena” in P. Grimal, The Dictionary
of Classical Mythology, Oxford (Blackwell) 1996’