@scsi:
top doesn't do anything on a per-site basis. I don't believe mytop does either; it can break down results by user, but I'm not sure if it can even summarize that.
gg? I can't find a man page for it, even on the 'net.
@Arashdn:
I presume you mean as a real-time report. If so, then unfortunately not. You can get limited server information from the admin login, and there are many tools you can use from the command line, but no one summary.
Jeff