Slavic myth is great and i have read a bit about it.
We don't really have stories of the gods (Perun, Volos), like we do from other myths, but there are many interesting folktales such as the Firebird and Vaselisa.
There also are a collection of short epics called byliny which tell the tales of such heroes as Ilya and Dobrynia.
Warner has a little book called Russian myths which is helpful.
And Bailey and Ivanova have an English translation of the byliny called Russian Folk Epics.
Ivanits has a great book called Russian folk belief which tells about such beings as the Rusalki and Domovoi, as well as Baba Yaga.
When King Vladimir converted to Christianity in the 10th C. in order to marry a byzantine princess, he through away all of the images of the gods into the river.