Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

There also appears to be a FedEx drop box in Terminal 3 at SFO, and FedEx 2nd-day service is acceptable to the IRS. But you'd have to visit irs.gov and enter "private delivery service" to get the correct street address for sending in a return via FedEx.