This is a pretty good deal to help you with the Christmas Challenge! Amazon changes their prices fairly quickly so if it is something you can use then be sure to grab it now. You can use your free gift cards from Swagbucks to pay for it!
Guitar Hero III: Legends of Rock Wireless Bundle $29.99 for PS3 (from $69.99)
Guitar Hero III: Legends of Rock Game Only $8.67 for XBox 360 (from $29.99)
Guitar Hero III: Legends of Rock Wired Bundle $29.99 for XBox 360 (from $89.99)
They are all eligible for free shipping.