Session Server for Windows
- Has built-in fail-over protection and load balancing. A session "sticks" to a session server not by IP as in the case of a local director, but based on session ID so that the browser is guaranteed to maintain its session. [Commercial]
- http://session-server.db3nf.com/session-server/session-server.asp

AuthentiX
- Authentication with AuthentiX and ODBC allows you to protect individual directories on IIS by asking browsers for their user's name and password. Your NT user/password database remains separate and private. By Flicks Software.
- http://www.flicks.com/flicks/authx.htm