Is there anyone who knows some good resources to use when researching mythology from various cultures and periods?

I am currently researching various races and making the mythology behind them. I have had a very nice trip into Celtic and Slavic mythologies but I know that there are many more races and stories that are worth researching but I need some good resources to see it. Thanks in advance!<br><br>Edit: I am talking about polytheism, like Greek, Egyptian, Slavic etc