Representing yourself is also known as pro se. Here is the definition from Nolo's Plain-English Law Dictionary:
Pro Se (proh say): A Latin phrase meaning "for oneself" or "on one's own behalf." This phrase describes a party to a lawsuit who represents himself or herself, without a lawyer. It is used in some states in place of in pro per (or in propria persona) and has the same meaning.
What you Need to Know About Representing Yourself in Court - A brochure produced as a customer service by the Pro Se and Customer Service Committees of the Colorado Judicial Branch.
Representing Yourself Guidelines - United States District Court - District of Colorado
Pro Se Resources - U.S. Bankruptcy Court, District of Colorado