What happens to my blog when I graduate?

Once you graduate your blog will be deleted 60 days from the date that your login has been disabled.

Can I take it with me?

Yes. Export it. You can use the built in export feature to export your site to Wordpress.com or to other blogging services as well. See Exporting Your Blog for instructions. Keep in mind that you won’t have access to the same plugins and themes that are available at blogs.evergreen.edu.

Another alternative to consider is to get your own domain name and host your own Wordpress installation. Several web hosts provide pre-installed versions of Wordpress and make it pretty easy to get up and running. With your own Wordpress instance you would be able to install any plugin or theme you wanted. See: http://wordpress.org/hosting/ for a list of recommended hosts that provide easy Wordpress hosting.