You have installed Raspbmc on your Raspberry Pi, converting it into a cool little HTPC. (Here is how to do that.) The Pi is running Linux after all and it is connected to the home network. Now, you want to SSH into it to explore its internals. That is easy.
In your Raspbmc, navigate to System → System info → Summary. Take note of the IP address (for example: 192.168.0.12) that has been assigned to your Raspbmc.
Ping your Raspbmc to make sure it is reachable from the computer you want to SSH from. For example: ping 192.168.0.12. If the ping does not work, check the settings of your wireless router.
Use PuTTY and SSH to your Raspbmc using its IP address and port 22.
At the login prompt presented by your Raspbmc use the username pi and password raspberry.
Bingo! You are inside your Raspbmc now. Have fun playing around with it 😊
Tried with: Raspbmc RC3