This Tampermonkey script adds options to StackOverflow to

1. expand answer box
2. expand code box
3. resize code font size
4. widen the entire page
5. remove sidebar

Source: https://github.com/yodog/userscripts/blob/master/stackoverflow-code-box-options.user.js

Install: https://github.com/yodog/userscripts/raw/master/stackoverflow-code-box-options.user.js

Feedback much appreciated

Update: now its not necessary to refresh the page to apply the changes.
Update: added several other sites from the stack exchange network.