I use one obvious app, and maybe a less obvious one, when I travel:
The Obvious one is Google Maps for Blackberry. Yes, I am the last person in the world still carrying a blackberrry... the app is not as good as the iphone version, but still usually gets me to my meetings on time.
The less obvious one is the Facebook for Blackberry app. I find that almost all of my friends and family are on Fb now. So with one simple status update I can tell anyone who wants to know (mom, wife, kids), where I am and that I am ok. It is not a well written app, as it doesn't access a lot of the functionality of FB, but when I am on the road, the simple status update is usually all I need anyway.