my main site (myname.com) is my portfolio and contact information. within that site i have a password protected subdomain - dev.myname.com, specifically for my clients (i am a graphic designer) to be able to upload/download files rather than trying to email them.
i have another subdomain, education.myname.com, that has my teaching philosophy, course syllabi, student work, workshop development, etc.
i also have another subdomain, process.myname.com, which i am just starting to slowly build an online archive of my past work that is focused on process, as opposed to just final "portfolio" quality work. this exists because...
...i have another subdomain, x.myname.com, that i am using as a framework for what i refer to as my "life's work" project, which is a research and design project that i intend to work on until i die. the point of this project is to develop a clear idea and maxim for my viewpoint on design theory, practice, and creation. it is online because i will be getting a lot of outside opinions and commentary from other designers and the like and this way it is accessible. the reason the above mentioned process archive is online is for the same reason; the life's work project will make reference to the process archive. the life's work and the process archive are just getting started this month.
i should note that i am not a web developer (not anymore anyway, that was another life) so these projects are strictly about the content as opposed to AJAX-y web 2.0 sexyness.