OFP was first officially released internationally, excluding North America, on June 22 2001. The official North American version was released on August 28th, 2001. OFP Gold and the OFP Gold Upgrade, which both include the new Red Hammer campaign, was released on November 29th, 2001. OFP Resistance is scheduled for release on June 28, 2002.
Besides your local software store, here are some places where you can order OFP from online. Be nice! I get a commission, at no extra cost to you, for orders placed from the links below. This helps offset my out-of-pocket expenses to maintain The FAQ.
A downloadable version of the OFP Gold Red Hammer Campaign can be purchased from Codemaster's OFP Gold Upgrade page. Unlike the OFP Gold and OFP Gold Upgrade CDs, you must already have upgraded to OFP version 1.30 before the Red Hammer Campaign can be installed from this download.