....
But really, your question is really vague. Please elaborate more on what you want to do. I can think of 10 answers to this question. Also please try the site search as well, I am sure your question has been asked before. Asking a question without thought or research into what you are asking is a pet peeve of mine.
Go to Google and do the following search:
site:www.webmasterworld.com subdomains
some serious info there, since in-house site search is , well err........
Shak
