Here are some $1 survival items no classroom should be without:
sticky notes - Ok, so maybe I just have a bit of an obsession but I use sticky notes for almost everything; writing a pass, sending notes home, book-markers, revising my students' papers, writing comments on student worker, etc. What I learned later in my teaching life was that my students didn't like it when I made corrections on their work. However, when I used a colorful sticky note, they loved it! I could have wrote the harshest of constructive criticisms and it worked every time.
socks - Yes, you can find them at the dollar store. You're probably wondering, "What for?" Socks work great for the whiteboard. I've actually found that they work better than the soft erasers. Also, if you get cute and colorful socks, it makes students want to help you erase the board. If you're using student mini boards during instruction, it's a great idea to have each student get a sock. I've found that one sock will endure for an entire year of erasing.
Ziplock bags - These are absolutely necessary. I have used plastic bags to store flash cards, separate game pieces, and for numerous class projects. They are actually the cheapest and easiest way for my students to keep their flash cards organized. Just use a Sharpie to write students' names on the bags.