If you're flying to your new location there's not a lot you can take other than clothing and maybe a stash of over-the-counter medicines so that you don't have to find a 24-hour pharmacy in a strange town in the middle of the night. If you take a computer of some type, you might want to take a printer, too. I bought a pilot's / carry-on piece of luggage, wrapped the printer in a new, fluffy bath towel to protect against bumps and jiggling, and filled in the gaps with computer peripherals like the back-up drive, program CD's, extension cord, and spare ink cartridges. I do carry it on rather than check the bag, but one time we were asked to check it at boarding time. I was really glad I had packed it so good!
An iPhone is a tremendously handy investment. You can get text messages, take photos, receive and send emails, send things to a wireless printer, and, best of all, you can get GPS map directions right on the phone. Check with your accountant to see if the cost could be tax deductible, too. Sometimes you might want to take pictures of problems with your accommodations as soon as you arrive so you have proof you didn't cause the damage during your 4-9-16 weeks of staying there. We have also used it to take photos of time sheets and send them by text message or email. You might want to download the "Pandora" app for free and listen to your favorite music! If your car has a cassette player you can even buy a cassette that plugs into your iPhone (or MP3 player) and plays over the car speakers. Check Wal-Mart for the cassette adapter - $5)
If you're driving to your new location, however, there's a bunch of stuff that makes life a bit easier for you:
An inverter that plugs into the car's power outlet/cigarette lighter. You can recharge anything that has a power cord by plugging it into the inverter. Some inverters even have USB ports that you can plug into for power. Wow. There are a LOT of things you can get now that run off the car's battery - from coffee mugs to small refrigerators!
Once you get to your new "home" your contract could be anywhere from two weeks to, well, a year. I pretty much pack it all in totes and load things in the car based on the length of the contract.
A good surge protector and a supply of extension cords that accept a 3-prong plug.
A small folding table of some kind to use as a bedside table, a chair-side table, a computer or printer table -- anywhere you need extra work surface or work space.
A tote with basic kitchen spices, some kind of ant-proof containers for a few cups of flour, sugar, corn meal, tea bags, coffee.
A small (or large) coffeemaker. Neither John nor I drink coffee, but he likes iced tea, and I like a cup of hot tea. We use the coffee maker to brew the tea.
A pitcher to mix juice, etc. in.
A quality knife sharpener. (In fully furnished places they may supply knives, but they usually aren't worth a hoot.)
We take a sleeping bag, spread it over the top of everything inside the van so as not to tempt anyone to break in and steal things, and then we use it as an extra blanket in the room.
Our own bed pillows. We're used to them and won't get a crick in our necks having to use someone else's. A good night's sleep is one of the imperatives of life. Bad sleep equals bad attitude.
For $100+ we have discovered gel-infused memory foam mattress toppers. They are amazing! And if you're a bit squeamish about sleeping in someone else's bed, this makes it almost like you're taking your own bed with you. This is seriously good stuff - weighs about 25 pounds! It will only take up about as much room as a good sleeping bag if you put some effort into rolling it up.
You might want to also throw in a wind-up flashlight and radio. These are things that we rarely use, so we never know whether batteries are good or not. The wind-up kind will get you through emergencies.
A tote for office supplies is nice, too. Printer paper, photo paper, pens, pencils, Sharpies, scissors, binder clips, paper clips, stapler, staple puller, post-it notes, scissors, Wite-out, scotch tape, masking tape, duct tape, manila folders, spare USB flash drives, an assortment of envelopes, postage stamps. It's only about $40 worth of stuff if you went out and bought it all new. Most of it you probably already have on hand at home. The problem is, when you need it, you need it - and that may be 11:00 at night.
Speaking of postage stamps... We have discovered that USPS usually has "Forever" stamps specific to the region you are in. Ask at the post office. For instance, in Virginia we bought postage representing the Civil War. It's just a fun family thing we do. Maybe the grandkids will ace a history test some day because of us!
Also, and very importantly, give some thought to your new mailing address. It can be a real pain if you're not 100% certain about it. One place gave us our address, but mail was being returned to the sender. Come to find out, the address didn't have a mailbox! The house number was right, but no mailbox. (Just quietly keep repeating, "Nothing in life is simple...")