(i)Paris offers you a Palm-sized guide to the Paris Metro system - something that any traveller to Paris needs.
It will help you find your way across the network, with more than 340 Metro and RER stations, all put into context with surrounding landmarks (airports, monuments, museums, leisure parks for example). A brief description/history of each landmark is offered, along with its address and telephone number.
Wherever you want to go in Paris, you will find the answer to your travel questions on (i)Paris. You can even request the quickest route between two locations, and (i)Paris will display the answer, complete with where to change Metro lines, number of stops, and the total approximate journey time. Useful information to have to hand when in a foreign city - and the creator of this program is French, so you can trust the accuracy of the information.
The graphics leave something to be desired, but then there is no need for fancy drawings of the Metro lines - what is important is whether you can work out where to go, and with (i)Paris on your Palm you won't have any problems there.