The software we used in class is Hallmark Card Studio. It is available in several versions, Deluxe, Standard and Basic. Several versions are available at Amazon. The standard and deluxe versions are also available directly from Hallmark for $30-$50 with free shipping. Finally, there is a basic version available from Hallmark for $10. The three versions are identical other than the number of greeting cards that comes with each package.
You can purchase heavy card stock in quantities of 250 from Office Depot here. You can also get 100 matching envelopes from Office Depot here.
Many stores sell smaller quanties of cards plus envelopes in a single package. Office Depot offers 30 cards plus envelopes in a single package here.