Hamachi

Simple and sweet! With Hamachi, you can organize two or more computers with an Internet connection into their own virtual network for direct and secure communication, including: LAN over the Internet, zero-configuration VPN, secure peer-to-peer, access computers remotely, use Windows File Sharing, play LAN games, run private Web or FTP servers, communicate directly, stay connected, and more!

http://www.hamachi.cc/

Virtual Wifi

VirtualWiFi is a virtualization architecture for wireless LAN (WLAN) cards. It abstracts a single WLAN card to appear as multiple virtual WLAN cards to the user. The user can then configure each virtual card to connect to a different wireless network. Therefore, VirtualWiFi allows a user to simultaneously connect his machine to multiple wireless networks using just one WLAN card.

http://research.microsoft.com