user management software - integration of entire site NEWBIE


Hello everyone,

I am a newbie and looking for something that can tie in all of my software together. I want it so that when a user visits my website and logs in to my phpbb forum they are automaticall logged into my classifieds( … _basic.htm) section as well and also my photohosting software and auctions( Whenever someone logs into any of the above or changes there profile in any of the above, I want the login or effected change to occur in all software.

Does anyone have any thoughts on this?
thank you all for any and all help,