session variables

I have WordPress installed in a sub-directory, because I have the website running(www.mysite.com and the blog http://www.mysite.com/blog). Is it a way to send session variables(such as username) from wordpress to the other pages of my website? I don’t want people to log twice on the same website. I was able to use session inside the blog directory but i can’t send it to the other pages of the website and the other way.
Thanks for helping