She goes through books like crazy, many times because she wants to go on to the next one before we're finished with the current one. Luckily they stock some in the patient rooms, and have a cart of books that is donated by customers of Half Price Books.
Snacks. When the visits get to be 3 - 4 long hours we get a little hungry. The clinic does provide snacks if you ask, and they always give her something on days when she has a procedure (i.e. lumbar puncture or marrow biopsy). There is no eating or drinking in the waiting room because there are always some children who are NPO (no eating or drinking) before their procedures. I am very thankful for this rule on days when she is NPO.
The portable DVD player - this has paid for itself many times over in terms of sheer enjoyment while she was inpatient and especially during ER visits. I take it to clinic now just in case we have an especially long wait in the patient rooms. On procedure days there is a DVD player in the treatment room and a personal DVD player on every chair/bed in the recovery room.