This is a two in one article actually. In a posting to today's cisco-nsp mailing list, Josh Horton provided a couple of links to his BlindHog Blog. His site has a wealth of good how-to articles for things routing and linux related. One entry that caught my eye was how to link router login AAA to a Microsoft IAS server. This basically does the job of a Tacacs server. Although it does the authentication and authorization, this Radius based authentication doesn't do the command logging that a Tacacs server can do. Even so, it is well worth a look. Other posts relate to ssh and some other router odds and sods.
The reason for his posting to the mail list was to advertise his wrapper for a Cisco router emulation engine at Dynagen. So for those studying for the CCNP exams and need a bunch of routers to check out OSPF, EIGRP, BGP and IGP, no need to spend thousands of dollars on real gear. Just get a recent IOS image and you can run multiple virtual routers all on your PC. The author says throughput is about 1kpps or so. But just to check out and test routing protocols with no sacrifice in command line options, this is an impressive capability.