I've always included an "about me" link on my portfolio site - but what I include there is always questionable, and changes with every version I make. I always put my resume as a link in there, and I often include links to non-graphic design work (all the other art that I do that I think is fun, and in a short description, I can tell someone a little bit more about me than what the resume presents). I design my pages so that no matter where a user goes in the portfolio, my contact information is always visible.
I've never had an official "bio" page - I never knew what to put in there or what the use of it would be to a client. If you have a philosophy about design, or a process you go through for providing services, you could include that in an "about" page. I'd include that info you mentioned - a sample of services provided, a link to your resume, and a "call to action" (contact me to set up a meeting...to learn more...etc).
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