I saw a super cute (huge) rainbow that was made of fabric that was folded over, hot glued and stuffed with cotton. Also,

• there are lots of cute fabrics with rainbow prints that you could use for bulletin board backgrounds. You wouldn't have to change it during the year because fabric doesn't fade like paper.
• You could use crepe paper (streamers) to make a fun, flowing rainbow on your ceiling or walls.
• Using rainbow clip art on your newsletters throughout the year would be cute. Add a rainbow screen saver to your computer.
• Print out actual rainbow photos off the Internet to post around your room. Different locations--great for geography/Social Studies. I did a google search for rainbow photos & there are tons of sites with amazing photos.
• Hang prisms from your windows/lights to ceate rainbows around your room.
• Post words to rainbow poems/songs/fingerplays on your walls.
• Use Skittles in a jar as a variation to marbles in a jar for discipline/behavior management.