Number Tiles are a really great tool.
http://www.montessorimom.com/downloads/number_tiles.pdf (match the number tiles with the dot tiles below).
Great Dot Tiles:
Use for ordering numbers, adding and subitizing. http://www.montessorimom.com/downloads/quantity_tiles.pdf
Algebra Tiles (SUCH AN UNDERUTILIZED RESOURCE)
You can either make number tiles or buy them commercially. They come in foam, wood and plastic. They come as squares or rectangles. They also make overhead number tiles.