I am new to silverstripe, and so far I love it. But, since I am new to it, I have a question. What I want to build is a small student community website, so I am interested if there is a way to have a website with forum, blog, downloads and wiki pages, and have all of them use a "centralized" user register/login system?
If you're using different software product and need a central registry with user credentials, I'd have a look at LDAP. Lots of products already support LDAP authentication (MediaWiki, vBulletin, ...) and for the ones that don't it shouldn't be too hard to write your own LDAP authenticator (see PHP LDAP functions: http://php.net/manual/en/book.ldap.php)