The purpose of this study is to determine the safety of lenalidomide (revlimid) in combination with fludarabine and rituximab and to determine the highest dose of lenalidomide that can safely be given in that combination. Lenalidomide is a drug that alters the immune system and may also interfere with the the development of tiny blood vessels that help support tumor growth. Lenalidomide is approved by the FDA for the treatment of two different blood cancers called myelodysplastic syndrome and multiple myeloma. Lenalidomide has also been studied in subjects with relapsed CLL. In this research study we are adding lenalidomide to a well-established initial therapy for CLL/SLL.