You may be reading about people using SSH to connect to their Pogoplug and wondering, "How do they FIND their Pogoplug?"
Your Pogoplug gets an IP address dynamically, using DHCP. That is to say, the IP address of your Pogoplug could change on a regular basis.
To locate the IP address, first find the MAC hardware address. Just look at the bottom of your Pogoplug for the MAC hardware address. This will be in the format of 16 characters, in 8 pairs, separated by a colon (":"). The characters will be 0-9 and a-f. Write this down. For your Pogodrive, the MAC address should begin with 00:25:31
Now, you'll need to look at your DHCP server and look at the client leases. One of the leases will have the MAC hardware address of your Pogoplug listed. That entry will probably not have a name, but it will have an IP address. For an IPv4 address, the address will look like 4 numbers separated by dots, like 192.168.1.101 or something similar.
For most users, the DHCP server will probably be your router. Usually, the DHCP leases are listed in a table in the "status" section of your router's web interface. If you are not sure, just do a Google search on "router-name dhcp table".
If you don't have easy access to the router's DHCP table, you can use a brute-force approach. Download an IP address scanner and have it scan your local network. This will have the affect of populating your ARP table (which is a list of all known devices). Again, look for an entry that begins with 00:25:31.
To make sure it IS really your Pogoplug, try to ping the IP address. (Yes, Google it if you don't know how.) Once you have managed to ping the IP address successfully, examine your ARP table for the MAC hardware address. The command to type is "arp -a". If you find a MAC address in the ARP table that matches up to your Pogoplug, you can move on to SSH.