Most routers will have the telnet port open. In cisco talk it is called their vty port or virtual terminal. And yes you can program and configure the router from this telnet session. The only thing I would mention is that there is no stored information on a router save the configurations such as has been mentioned earlier. The cool part about routers is that you can block or permit pretty much any port either by name or by port number and also the same with any IP address. I mean ANY ip address. Of course there are ways around that.

Now word of warning. If you change any configuration on a router it will automatically log your ip address and state that changes have been made from that ip. (again there are ways around this as well but if you need to do that you probably shouldn't be in the router.) Ohh, if you do change router configurations illegally and get caught you are facing some really hefty fines. Depending on what kind of router you jack up and how long it takes people to fix the problem. Now if you drop a huge backbone router, (as if it would be possible to get into) but just speculating that you did it. They would lock you up and throw away the key. (that is if you are lucky)

But if you are interested routers don't cost that much and they are cool to have on a home network.
Hope the you like the info. Enjoy!

Ohh, before I finish routers have their own OSs. Cisco uses its own cisco OS nothing like UNIX or Windows. A whole new animal. Some essential commands can be found on their website though.

you can use the "?" or the "show" commands they work kinda like "dir" for DOS