I am not an attorney
It is my understanding, that as of 2006 there is an exemption of federal tax upon death of 1.5 million and that it will increase to 2 million. So if your estate is less than those figures, you can right your own will using the free forms on this site. If your estate increases or is higher than those amounts, you will need to do some estate planning that may involve a trust, which means at that time you may need a lawyer. If you dont want to spend a lot of money on this, then take the time to read the info on this site.
Also, as of 2011 the exemption will go back down to 1 million, so if you estate is worth more than 1 million, you will have to revisit your estate planning.