Evaluating PHP scripts for use on one-login site

Hi guys-- New user of PHP and MySQL, already making headway in a very short time and am astonished at how totally cool it all it. As always when I learn new stuff I'm jumping in to the deep end--or at least it seems like the deep end to me. :) Basically what I want to do is offer a range of services to my website users and have them only have to log into the site *once*. I'm seeing tutorials etc on authentication/tracking, well and good, will do. What I would like is some advice on how to evaluate existing scripts (like chat, bulletin boards, etc) for integrating into that type of system. What, if anything, should I look for? I'm not at all averse to figuring out how to tie things together myself, but it would be nice to hear what to do and what NOT to do from experienced folks who've done it--things to watch out for, if there are such things. Regards, Lynn -- Siprelle & Associates: Distinctive Web Design Since 1994 Lynn Siprelle, President: Newest Associate Josie born 9/9/97 Business: lynn@siprelle com | Personal: lynsa@siprelle.com Portfolio: http://www.siprelle.com/ | TNH: http://www.newhomemaker.com/