The “hook_html_head_alter()” can let you add tags to the HEAD section of a Drupal page. Despite some of the comments, I found that if you need to put it into a module in Drupal 7, you do need to name the hook after the module’s name, instead of just “template_“….
If you want to build tags… the Drupal way :-P… try the function theme_html_tag().
I found this was useful for a module I was writing… stay tuned people :-).