Many will routinely send your resume to companies without your knowledge. Have the agency clarify its policy in this regard. If this is a suitable marketing channel for you, contact as many agencies as possible for maximum exposure. There are also special fairs for new college graduates. This is a way for you to see several potential employers at one time and for them to save recruiting costs.
Some fairs require advanced registration.
They are usually advertised in local newspapers and at university career and placement offices. IU Southeast sponsors or co-sponsors five fairs per year.