You can try to track down the company who owes you money, but if your agreement was with a company that was incorporated (or formed an LLC) and the company is now out of business, the likelihood that you will actually recover what you were owed is slim.
However, if you performed services for an individual who was simply using a company trade name, it may be worth going forward with a collection lawsuit as any judgment you get will be on the books (and collectible) for a number of years.
In addition, if you were really performing employee-type services (and were misclassified as an independent contractor), you may also have some recourse against the individual company owner for failure to pay wages.
It's best to confer with a litigation attorney who has experience in employment and collection law to assess the costs and likelihood of success, depending on your true situation.
Nina L. Kaufman, Esq. is an award-winning New York City attorney, edutainer and author. Under her Ask The Business Lawyer brand, she reaches thousands of entrepreneurs and small business owners with her legal services, professional speaking, information products, and LexAppeal weekly ezine. She also writes the Making It Legal blog.