Augmented Reality Libraries

To develop an Aumented Reality application you need libraries. Below is a list of libraries for different plattforms:
Stand Alone Application Development:

• ARToolKitPro: C/C++ marker based tracking library
• ARToolKit NFT: C/C++ markerless tracking library
• NyARToolKit: Java/C#/C++ optimized marker tracking library
• osgART: C++ rendering and interaction library
• FLARToolKit: Actionscript (v3) version of ARToolKit

Web Application Development:

• FLARToolKit: Flash version of ARToolKit
• FLARManager: High level Flash AR library
• SLARToolKit: Silverlight port of ARToolKit

Mobile Application Development:

• ARToolKit for iOS: iPhone port of ARToolKit Pro
• AndAR: Android port of ARToolKit Pro

Of all the above I would recommend opensource AR from http://www.artoolworks.com.