VWR has a stockroom in 56-068. You can pay for items with you MIT credit card there. The phone is x3-1881. A list of what is available is accessible from the VWR page on ECAT
Chemicals are in a different location though, E25-169. This room has limited hours, 1:30-3:00pm. Certain chemicals, such as pure ethanol, must be paid for with a signed requisition form.