Linux media player
I made a much lower-tech personal version many years ago, as an IT Peace Corps volunteer. Mine of course was (a) very low cost and (b) designed to travel stuck in side-pocket of a backpack on a crowded country-bound bus. OK, it was really just a few screwdrivers, a 3-2 prong electrical adapter, and a flashlight.
I also always carried around:
1 ~3' crossover cable or crossover adapter (no faster way to test networking!)
1 multi-head cable tool (the kind with a core USB retractable cable and a pouch of other cable-heads to turn it into a phone, network, mini/micro/device USB, firewire, etc. -- easy way to carry around "the right cable for the job" when you're not sure what today's job might be)
My favorite toolkit items were more around the software end of the spectrum, though:
1 bootable USB stick with DamnSmallLinux and a PortableApps Suite
1 bootable floppy with WinXP/NT admin password reset tool
1 BartPE bootable XP CD with anti-virus and diagnostic tools
1 Knoppix or other Linux LiveCD that will work on a wide range of hardware and let you extract files from the HDD
1 CD and USB stick of common free/shareware/OSS software tools - anti-virus, various anti-mal/spy-ware, registry cleaners, zip/archive software, OpenOffice, PDF creation tools, and so on.
Just a quick note: Ubuntu 10 totally rocks. Better digital video and audio support (via HDMI and toslink) than Windows 7, slicker than Mac OSX with a great dock and productivity-enhancer with gnome-do/docky, tons of crazy user interface enhancements, a smooth 3D desktop... the list goes on. It's amazing, and it's open source.
I finally broke down and bought a laptop, as my existing bevy of half-working laptops is now seriously impacting my ability to actually get things done, as opposed to yak shaving in order to fix the random problem of the day.
Here's a quick tour of my harem of laptops:
A "desktop replacement" system that was cutting edge ... seven years ago - which is surprisingly still my "prime" system.
The "get me through grad school" system that was grabbed off of DellAuction ... four years back, which now has a hard drive which smells of impending FAIL and a hinge which is held together with metal glue
My indefatigable Dell Latitude which I got at the liquidation auction of Agillion in 1999, which traveled with me from Austin to Venezuela to Jamaica to DC, and has had Win2k, 98SE and various flavors of Linux running on it.
Last but not least, my OLPC, which I have a soft spot for, but it's not exactly super-fast itself)
The laptop (a Lenovo Ideapad) has arrived, pre-installed with Windows7, but I am doing my best to not use it much. I'm waiting for Ubuntu 10 to come out tomorrow and see what craziness I can get into there.
My get-me-through-grad-school system is currently running Ubuntu, but isn't quite up to the task of my expectations (I love running all the eye-candy available with "Compiz", which you can see an old demo of at youtube.