User Information Gathering & Relationship Management (Registration Processes that are less of a bother and other ways)

Hi there,
I'd like to invite you guys to share opinions, methodologies,
experiments, examples of successful ways of getting the user's
information through a registration process or other (more playful)
ways.

I'm preparing a case study and later a guide for a standarded
internal registration process and try to look at it from every
possible angle.

Your thoughts are gonna be highly appreciated.

Andreas