I like the idea of learning by computer!  Keep me posted about what you find. 

Below you will find information about vocabulary cards.  I'm sure you can find them on Amazon.com or at any university bookstore where Portuguese is taught.  The cards have English on side and Portuguese on the other.  They are good, but... what you are doing now may be even better because you are finding the words in context.  I know you are looking for a better way, but it sounds to me you have found an effective way to improve your language skills.

Portuguese Vocabulary Cards (Portuguese Edition) by Vis-Ed (Visual Education) (Cards - Oct 1, 1997)