There are some currency converting software for desktops, but I rather ignore them (for now) and consider the free applications for mobile phones (smartphones) and tablets. The reason is very simple: the travelers need ther mobility, it easier to get your smartphone or tablet than a laptop or a netbook and use is applications. You can do it everywhere you have phone signal or Wi-Fi.
BlackBerry Currency Converter and Exchange Rate Service
Convert currencies on your BlackBerry, with correct, up-to-date exchange rates automatically handled. View sums in several currencies at once. Get automatic exchange rate updates for 160 currencies – delivered and stored on your phone. Simple conversion tables make it easy to price items in any currency you wish.
You can find more information here.
XE Currency app for BlackBerry
Convert every world currency on-the-go with the XE Currency converter for BlackBerry by XE.com. With live up-to-the-minute rates, this currency calculator is simple, powerful, and FREE! With more than five million downloads, XE Currency has been featured by the BBC, CNN, the LA Times, and The Travel Channel!
Download link and developer website.
OANDA currency converter for Android
Free currency converter uses OANDA Rates®—the same daily filtered exchange rates used by auditing firms and banks. Convert 190+ currencies and four precious metals. Choose the Interbank rate, or use the percentage add-on feature to calculate typical rates charged by credit card companies and banks.
You can download it from here or search for more information on developer website.
PocketTools Currency converter for Android
Simple Currency Converter that tracks currencies from around the world. Easily convert between your favorite currencies. Graph currency pairs over time, get the latest news on each currency. Set up portfolios of currencies for easy tracking.
Download link and developer website.
Xchanger 1.23 (S60 3rd) currency converter for Symbian
Softonic had put online a review and a download about Symbian's version of this software: Xchanger is a web enabled converter that will convert between any world currencies. It's a simple application to use, with a nice graphical interface. There is maybe one too many screens when you make a conversion - Xchanger asks for too much conformation from the user in general.