Agendas.

Agendas are one of my top essentials whilst traveling. I use it to write down address as well as travel details.
My boyfriend keeps asking me why I don't use my blackberry or macbook that has a calender built in. But I just have to be able to write it down and have it on paper, I'm old fashioned in that sense.

Plus, I hate to admit it, but his iphone is better for calenders than my blackberry is.