Deserving its own mention is my favorite casting (so far) -- Vanessa Redgrave as Eleanor of Aquitaine. I think she's possibly the only actress who can be as formidable in Eleanor's crown as Katharine Hepburn.
Now, The Hollywood Reporter says that William Hurt is joining up as William Marshall (or Marshal if you keep the historic spelling), a man described as "the greatest knight who ever lived" by his contemporary, Stephen Langton. He rose from obscurity to become a knight, who made his living in jousting tournaments a'la The Knight's Tale. He joined the court of Henry II and subsequently served the three following Plantagenets, including King Richard I, and his brother, King John. When he died, he was one of the most powerful men in Europe, and was known simply as "the Marshal."
Given the quasi-historical spin Scott is giving the story, I'm guessing Hurt and Russell Crowe's Robin Hood will butt heads. After all, Marshal was an Anglo-Norman who threw his support behind the Plantagenets who were decidedly foreign (he even backed King John against the Barons post Magna Carta), and Robin Hood is an Anglo-Saxon watching his native people being pushed out of power. Despite all the "revisionist" talk, this is really classic, old-school Robin Hood that books such as Ivanhoe and The Once and Future King borrow from rather than the Prince of Thieves pop culture knows him as.
Now I seem to be one of the few that's shamelessly excited for it (and I should know better, I'm burned by these kinds of movies all the time) but even if you aren't, you can't deny they've lined up a fantastic cast. Hurt and Crowe sparring should be worth the ticket price alone, right?