Wait a minute, Kate from Lost is in this movie?!?! How did I miss that?
Yep, she plays a Peter Jackson made up Elf, Tauriel. Although given the way the movies may break up into 3 parts, I suspect there is a chance that she might not show up until Part 2 and Part 3. Of course, PJ managed to work Arwen into the Two Towers movie even though she never appeared in that book so I don't presume to be correct that Tauriel would be limited to only the later chapters.
(image taken from box art for a toy)