Sign the petition if you haven't (https://petitions.whitehouse.gov/petition/pardon-edward-snow...), and don't stop there: write letters, make phone-calls, visit your officials' offices, get involved at the party level and see about pushing things there, give money to organizations like the EFF. If anyone else has other suggestions (or more details about how to do any of the above, or interest in coordinating any of the above), please add!
[1] Congressional oversight is a joke when money is so important in politics and the only people who will know about the decision are the contractors who will be contributing to your or your opponent's campaign next cycle based on whether you let them keep the contract.