Want to View Switch Config

I want to view the configuration (IP address, name, VLANs, etc.) of a couple switches with unknown IP addresses. For other switches with known IP addresses I used PuTTY to Telnet to them and run some simple commands, no problem.

How can I find the unknown IP addresses of the other switches so I can do the same thing? Or is there another way I can look without using Telnet?

The switches are Cisco 3750G, 3750E, and 3550.

Thanks!