questions on SSL

[s0h0us () yahoo com]

I'm lookig for some comments regarding using SSL to encrypt connectivity to entire website as opposed to just certain 
critical connections such as an online banking link at a financial institutions. is this a more common practice now? 
Bandwidth wouldn't seem to be as big an issue as it was in the past with dialup connections. 
Can one SSL certificate be used to encrypt multiple links originating from the same site:
https://x.domain.com
https://y.domain.com

thanks for the feedback