William Morris (1834-1896) is often credited as being one of Tolkien's literary influences. Probably because Tolkien said so himself:

"Amongst other work I am trying to turn one of the short stories [of the Finnish Kalevala] . . . into a short story somewhat on the lines of Morris' romances with chunks of poetry in between."

"The Lord of the Rings was actually begun, as a separate thing, about 1937, and had reached the inn at Bree, before the shadow of the second war. . . . The Dead Marshes and the approaches to the Morannon owe something to Northern France after the Battle of the Somme. They owe more to William Morris and his Huns and Romans, as in The House of the Wolfings or The Roots of the Mountains."

I haven't read The House of the Wolfings or The Roots of the Mountains but I plan to someday. I would however like to know a little bit more about Morris. If you have a recommendation as of what book is essential to get an introduction into this writer, and especially his influence on Tolkien let me know. There are so many books out there I don't know where to start.

Also is anyone collecting his books or other writers that influenced Tolkien? I think it might be a great way to add value to your Tolkien collection.

For more information about the relation between Morris and Tolkien, I would recommend you to have a look in The J.R.R. Tolkien Companion and Guide - there's an entry in Reader's Guide for William Morris (pp. 598-604).

I'd second Morgan's recommendation, I think the Companion and Guide is indispensable for all members of this site.