This study is being conducted to evaluate the overall safety of lenalidomide (also known as Revlimid) in patients with lymphoma, and to determine whether it is effective in preventing this disease from returning after stem cell transplant. This study will also determine the dose of lenalidomide that can be given without causing severe side effects. Lenalidomide has not been approved by the U.S. Food and Drug Administration (FDA) for the treatment of lymphoma. At least 28 people will be enrolled on this study at the University of Pennsylvania.