Here's some thoughts on support gear you may want to include in your EDC bag, to help keep your electronics up and running.
Low-tech Backups: Laptops are great for note taking, but I like to have a pencil and notepad for handwritten notes as well. Some kinds of notes are just easier to draw out or need to be quickly jotted down on the spot, and a small notebook excels at this. It also provides a backup in case your laptop craps out on you--dead battery, whatever. I like the Moleskine Cahier
Spare Batteries: For flashlights, phones and perhaps your laptop (though laptop batteries are heavy). Keep your gizmos running longer. I carry 8 AAs and 3 AAAs in my kit; probably overkill on the AAs, but four of them ride in a battery backup device (see below).
Battery Backup: Rechargeable backups like the Tekkeon Tekcharge are great for charging phones and devices with built-in batteries on the go. The Tekcharge has the added benefit of working as a battery charger for rechargeable AAs. I don't use mine very often, but it comes in very handy when I do need it.
Car and Wall Chargers: I like the current crop of chargers that have a USB jack, which you plug your normal USB cord into for a charge. Gives you some versatility, vs. need a different charger for each device.
Cables: I carry a mini USB cable for charging my TekCharge and connecting portable hard drives (if needed) and a short iPod cable for charging/connecting my iPhone. I plan to add a few extra cables here--CAT-5 (network cable, for troubleshooting mostly), HDMI cable for connecting my laptop to TVs.
Microfiber Cloth and Cleaner: I have a big, freebie microfiber cloth that I use basically on a daily basis to clean screens, devices and glasses. Weighs nothing, gets used all the time. The cleaner is for really dirty screens and gets used less often.
Wireless Mouse: If you use a laptop a lot, the little touchpad gets tiring quickly. I carry around a small-ish Logitech wireless mouse
Headphones: I actually carry two pairs of headphones - a good set for daily use and a cheap-o set for backup/when I forget the good ones.
Phone Headset: I'm not a blue tooth person, so I just carry a dollar store/freebie wired headset. If you need to talk on the go, while driving, etc. these are a big help.
Mini Surge Protector: If you often have concerns about the quality of a wall outlet or need to plug multiple devices/share a wall jack, these are pretty handy. Most have a couple USB slots and can double as a wall charger. The Belkin
Portable Hard drive/USB Drive: I carry an 8gb USB drive, loaded with a few useful PortableApps and some encrypted files. Mostly, I use this to transfer large files around. On trips, I will occasionally add a 1TB portable hard drive loaded with movies. If you do a lot of photography, this might be a must-have for you.
Spare Flashlight: My EDC flashlight is an untactical Fenix LD01
Spare bulbs: If you carry an incandescent light and can't/won't switch over to LED, it'd be wise to carry a spare replacement bulb.
Mobile Wi-Fi Hotspot: There are several of these on the market, the Sprint MiFi
EDITED TO ADD: Having a portable copy of Linux (Damn Small Linux is a measly 50mb) is very useful if Windows gets corrupted and you need to get into your machine and access/back up your files. Also, BACK UP your data and keep a boot disc and your machine's drivers close by.
What did I miss out on? Any other support gear to consider? What do you carry? Comment.