Stem Cell Transplant in Treating Patients With Hematological Cancer or Other Disorders

RATIONALE: Giving chemotherapy, such as fludarabine, busulfan, and cyclophosphamide, together with antithymocyte globulin before a donor stem cell transplant helps stop the growth of cancer and abnormal cells. Giving chemotherapy before or after transplant also stops the patient's immune system from rejecting the donor's stem cells. The donated stem cells may replace the patient's immune cells and help destroy any remaining cancer and abnormal cells (graft-versus-tumor effect). Sometimes the transplanted cells from a donor can also make an immune response against the body's normal cells. Giving cyclosporine and mycophenolate mofetil after the transplant may stop this from happening. PURPOSE: This phase II trial is studying how well stem cell transplant works in treating patients with hematological cancer or other disorders.