I have created a platform on my aegir dev server and I found myself wondering once the platform in drupal7 is installed is there a way to create websites using that platform via the commandline.
Yes there is: it's a two or three step process, but automatable.
Step 1) Create a Drush alias, or in Aegir terminology, 'context' for the site using
drush provision-save (arguments)
Step 2) Install the site using
drush @(site context name goes here) provision-install
Step 3) (optional but recommended) Verify the platform in the Aegir interface to have it automatically detect the site and 'import' it into the frontend so that you can do other things to it later via the web interface. You can also run this verification from the command-line with
drush @hostmaster hosting-task @(platform context name goes here) verify
For specifics on the syntax of provision-save etc, see my article, "Manage your Aegir system from the command line": http://mig5.net/content/manage-your-aegir-system-command-line.