[yoz-y]

You could print the cards out of the Gatherer or some other sites. I think there are even programs that can create sheets for that.

There is also Apprentice, kind of like MtG online but with barebones interface, that allows you to play against other people.

[lelandbatey]

To expand with more detail: there are several sites which let you enter a lit of cards and they'll generate printable PDFs which, when printed on paper, are meant to be easy to cut out. For example:

http://www.mtgpress.net/

Then, you simply slip your rectangles of printer paper into a card sleave with a real Magic card (usually some card you don't care about such as a basic land) and tada, you've got whatever cards you want and all it cost was ink and time time.