How do I programmatically install and enable a module? There is a lot resource for doing it in Drupal 6, but I didn't find a solution for Drupal 7.

How can I install and enable selected modules?
There's just one step, using module_enable():

$modules = array('module1', 'module2'); // Array of module names
$enable_dependencies = TRUE; // Whether or not to enable dependant modules

module_enable($modules, $enable_dependencies);