Cpanel is widely used by web hosts and has their own documentation. There is also a link to it at the bottom of each page in Cpanel.
Each webmail program has it's own support site: RoundCube and Horde.
Cpanel allows you to install many progams like Drupal and Joomla that maintain their own support sites. Click over to the 1-click install list for links to these sites.
We recommend Wordpress for blogging and even for many regular websites. It's easy to install from our control panel - just scroll down to the Softaculous section and look for the WordPress icon.
If you need inspiration or blog development help, Problogger is a great resource.
If you have a question about WordPress, Wordpress Answers is another great resource.
For more advanced issues, the Pro Webmasters Stack Exchange is a good forum to search for answers and ask questions.