An offer in compromise, also called an OIC, allows you settle your tax debt for less than the full amount you owe. It may be a good option if you can't pay your full tax debt, or doinf so creates a finacial hardship.
Offer In Compromise Pre-Qualifier
Use this tool to see if you may be eligible for an offer in compromise.
Offer In Compromise Application Form (Form 656 Booklet)
Forms and instructions for applying for an offer in compromise.