When beginning my sophomore year at RPI, I thought it was about time I built my own computer. My trusty Thinkpad was still serving all my personal computing needs, but I was starting to envision fun uses for a dedicated server. My jet-setting college lifestyle necessitated that the computer be built into an aluminum briefcase for easy transport.
Even though it was my first computer build, I knew the assembly of the computer would be simple. It was integrating into a custom case that freightened me. From the beginning, I was fairly certain that I would foul things up (usually my visions included a fractured motherboard). For this, I designed a budget system, with an Intel Celeron processor as the core. Unfortunately, it wasn't until just after purchasing the hardware that I would take a course (Computer Organization with Christopher Carothers) which mathematically detailed exactly why the Celeron's low price is not worth it. Oh well!
Despite my worries, the process was really very simple. I screwed the motherboard, power supply, and hard drive to an aluminum sheet, which I then attached to the briefcase. This ensured that all the components were properly grounded.
Airflow was the only other concern, and I placed a single intake fan (with blue LED's, of course) directly over the hard drive. The air flows from the hard drive, across the mother board, and out of the case via the power supply's fan. This clockwise current is encouraged with a wall isolating the hard drive from the power supply.
Because of its portability and headless nature, I set up dynamic DNS through No-ip.com for the briefcase. This meant that I could carry the computer with me anywhere, plug in power and ethernet, and http://briefcase.no-ip.com would resolve to the server (barring firewalls, of course).
Over the years, the briefcase has served as a private file server for my friends, a media server for my family, and a personal Linux test-bed (it was my first Linux computer, after all!). It is currently gathering dust, but I do like to take it out from time to time when I'm feeling like spy.