Buy.com has the D-Link DWA-160 Xtreme N Duo USB Adapter for $59.99. This adapter ships for Free, and it features:

• Delivers up to 14x faster speeds1 and 6x farther range than 802.11g
• Xtreme N Duo technology enables HD video streaming, file sharing, enhanced Internet phone calling (VoIP), and Web surfing
• Access a secure wireless network using advanced WPA or WPA2 encryption
• Easy to install and use with the D-Link Quick Adapter Setup Wizard or using Wi-Fi Protected Setup (WPS)
• Backward compatible with 802.11g devices including game consoles and digital media players