I did a How I Work interview for Lifehacker, where I talked about the tools I use, and how I use them:
What apps/software/tools can't you live without?
Ubuntu and the suite of GNU tools in any robust Unix system. A good text editor (currently Gedit)—I keep all of my working files at .txts. A robust, highly configurable browser (Firefox/Firefox for Android). A fast RSS reader (presently Google Reader, likely to be Newsblur next). A tetherable mobile connection—I use EasyTether for Android to circumvent tether-blocking as deployed by some of the carriers I use around the world, especially Rogers in Canada. AirDroid for moving files on/off Android devices in my life. An external USB battery (currently PowerGen 5200mAh External Battery Pack).
A rugged, roomy, weatherproof backpack (currently a Bagjack Skidcat). A moneyclip. A small, six-card credit-card wallet. LibreOffice spreadsheets for bookkeeping. GPG, cryptsetup, and TrueCrypt for information security. A high-performance mailer with functional scripting engine (currently Thunderbird with a ton of rules and a huge black-listed kill file and white-listed address book). A titanium Widgy keychain prybar (pictured at right)—useful as a pocket knife but flies (heh) under TSA/BAA radar. No-name, easy to replace earbuds with integrated mic for phone. Exeze waterproof MP3 player for swimming. AquaSphere Seal swim goggles—I swim everyday for about an hour and listen to last night's CBC's As It Happens news podcast. Exeze + Aquasphere are a reasonably priced, reliable goggles/MP3 combo. GoToob silicone bottles for shampoo/soap for the pool—these have strong, reliable suction cups that stick them perfectly to the shower wall.
A no-name, cheap mini screwdriver set—I get these confiscated about six times a year by airport security, especially the jerks at Gatwick airport, but it's worth buying a new set every time. Catering-sized sachets of Tabasco—these don't show up as liquid on airport scanners, unlike the mini bottles. I put Tabasco on everything. I'd use it for contact-lens solution if I could. Aeropress—the single most versatile and reliable way of making coffee, especially on the road. Perfect when paired with a Porlex hand-grinder.