Hi Ben,
Yes, Cisco has a product called Secure Access Control Server (ACS). It's their version of a RADIUS server. It is capable of authenticating directly with NDS (I know this for a fact). It's rather easy to learn and use, and is flexible and powerful. It is available as software for you to run on a server (Windows or UNIX), or as a hardened appliance (ACS Solution Engine).
Check out more info here: http://www.cisco.com/en/US/products/sw/secursw/ps2086/index.html
The appliance works very well, and basic configuration is a breeze.
Good luck. I hope this helps!
- Jay