The look and feel (as defined by the theme we use) can also be used to communicate with our users. The following are some examples of what we could do:
Display links to any mobile applications which we may have, if we detect the user is browsing the site on their mobile device
Add a simple bar of information to the top of the site, perhaps relating to a specific feature
Add (graceful and unobtrusive) information pop-ups using CSS (cascading style sheets) or using JavaScript libraries such as Fancybox (http://fancybox.net/)
Adding a collapsible message, where the user can click an icon to expand an administrative message, which we can periodically update
These options require knowledge of HTML, CSS, and Drupal themes.