Currency Converter for Mac and iPhone

This widget is extremely helpful when I'm planning international trips.
http://www.apple.com/downloads/dashboard/calculate_convert/currencyconverter_palplesoftware.html
A currency converter for iPhone is also available.
http://itunes.apple.com/app/currency-converter-hd-money/id290527470?mt=8

Siri Assitant for travel

Have Siri remind you.  Now that I'm using the iPhone 4S I am so glad to have Siri helping me stay organized.  From what to bring on my trips, to setting up meetings, calling clients, and making reservations. Adding reminders and calendar events makes my life that much easier.  http://www.apple.com/iphone/features/siri.html

Timezone Conversion widget for Mac

Timezone Conversion

Useful timezone converter (widget) I keep on my Dashboard.

Travel checklists

I have come up with multiple travel checklists that I save on my iPhone, iPad, and MacBook  (using iCloud) and edit whenever I need.
Here is a link to David Allen's (Getting Things Done^® system creator) travel checklist:
http://www.gtdtimes.com/2010/03/14/david-allens-travel-checklist/