As noted previously, if you choose to default before the end of the day today (in this case, 11:59 PM PDT), you are welcome to participate again next year, though you might not receive a gift if the person assigned to you also defaults. If you choose to default tomorrow (or afterwards), you will not be able to participate again next year. If you have to get off this particular bus (or train, plane, etc.), this is the day to do it.

The handy-dandy pinch hit list is located here, and the equally handy-dandy beta list is located here.