We know that we need to have language every where in a preschool classroom. Kid's learn by osmosis at the preschool level, and seeing written language strengthens pre-reading skills. So a great way to advance pre-reading skills, and help promote self help skills is classroom labeling.
When you label items in your classroom it helps to have the word and picture. This helps the children understand the correlation between these symbols and the spoken word.
Another great reason to label in your classroom is clean up time. When a child can put things away on their own it gives them a sense of self sufficiency and pride. Besides it makes it easier on you. If they can pick up themselves then YOU don't have to do it all.
I found a great place to help this endeavor- Environments. They have resources for teachers that you can make up on their site and print out. You do have to register for a free membership but isn't worth it.