the messy bun is definitely very easy and very much in vogue.
so is the messy braid, as well as the half up and half down hairstyle. all very very easy to do and carry, even when you are on the go.
here are two hairstyle DIY links you'll love :)
http://travelfashiongirl.com/5-easy-travel-hair-styles-for-your-next-trip/
http://www.marieclaire.com/beauty/hair/how-to/g2614/10-easy-quick-hairstyles-in-10-seconds/