I notice that the site has a creative commons license.
Does this also mean that any user code placed on the site is also released by a creative commons license?
Yes, any user contributed code is released under the CC BY-SA.
From the ToS ( http://stackexchange.com/legal )
You agree that all Subscriber Content that You contribute to the Network is perpetually and irrevocably licensed to Stack Exchange under the Creative Commons Attribution Share Alike license. You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content and to allow others to do so in any medium now known or hereinafter developed (“Content License”) in order to provide the Services, even if such Subscriber Content has been contributed and subsequently removed by You
So, the key parts. You grant everything to SE under a CC BY-SA license. You can never revoke that grant. (As Josh points out) CC BY-SA allows you to use and abuse, even for commercial work.
One interesting exception is SE's Network Content. That portion, which includes a source code clause, is NOT released under a CC BY-SA. That section allows for personal use of the NC. Keep in mind that Network Content != Subscriber Content, so it's really a non-issue unless you like to obsess over those details.
I believe that is correct as code is included in the content.
to Share — to copy, distribute and transmit the work
to Remix — to adapt the work
to make commercial use of the work
Anything that you post to StackOverflow will be under the terms of the creative commons license. You can find more info by looking at the bottom right of the page and clicking the cc-wiki.