The Pentacle is used at the center piece, and serves as a protection piece for your altar. The five points of the Pentacle are often labelled (starting at the top) as Spirit, Earth, Air, Fire, Water. You can use other symbols, but this is by far the most popular.
Representations of the God and Goddess. You can use candles, or you can use status. Really any symbol that has meaning for you will due. The most popular is pillar candles, and that is what I like to use. You can use multiples of any a candle and statue for both the God and the Goddess. Really its just up to personal preference.
A Chalice, looks like an extravagant wine glass. The Chalice is a representation of the feminine powers, and usually holds water and represents, well, water. It can be made of any material you like, many people use silver because it represents the feminine moon powers more.
Bowls filled with various things depending on what you need for your ritual. For example a bowl of salt, and you can use that salt as a cleansing element.
A cauldron. There is not a cauldron pictured above but I find that it is a necessity for myself. It represents femininity and fertility. It is a common tool used for brewing and cooking. You can also use it as an incense burner, to contain small fires, and as a tool for divination.
Anthame (pronounced aa-thuh-MAY), is a very traditional tool. This tool is used to prepare all of your materials, such as herbs and spices.
Wand is one of the most traditional tools in a witches cabinet. Most witches make their wands from elements in nature. Above all the wand should feel good in your hand, the power and vibrations of it should agree with you intentions for it. The wand is traditionally used in invoking the God and Goddess, direct energy, and empower objects. You can also use it for more conventional purposes like drawing symbols in the earth or stirring the cauldron. This tool is associated with fire.