Printable bookmarks are another staple of my library centers. I have a stack of bookmarks, together with colored pencils and Twistables crayons (much less messy than regular crayons--but don't buy the Twistables colored pencils--they break VERY easily!)
I have a sign stating that students may color ONE bookmark (otherwise some kids will stuff ten into their folder, and I'll spend all day copying and chopping up bookmarks!) Sometimes, instead of leaving a stack at the center, we hand out a bookmark to each student at checkout Then they can take it to the bookmark center while they wait for others to check out their books.
I have been amazed by how much kids of ALL ages love to color a bookmark, personalizing it to their own individual style. To me, this just adds more fun to the whole reading process and the experience of a library visit. I suppose we could say we're developing fine motor skills, but I'm happy just knowing that this library center makes students grin as they walk in my door!