Yes, the simple way is to ask for the users you want to add to ensure they have an account over at the PC blog site:

http://psychcentral.net/signup/

One of the options during signup is to just register a new account, or get a blog. If your users don't want their own blog, they should choose "Just a username, please." Once they're registered, you can add them to your blog to create a community blog.

DocJohn