Another way to play this great game online.
You can purchase it on Steam for a few bucks (tip: don't buy those foil things because it'll make your rares looks unreversably annoying).
In Duels of the Planeswalkers you can play a good number of pre-assembled decks against various computer opponents (decent AI) or human players. It's possible to play 1 against 1, 2, 3, two headed giant games, or archenemy (as an archenemy or against it with 2 other players). Another feature are challenges; specific pre-built situations where the player have to make the best decision so he can win in one turn.
I'm having much fun with it. The cpu quests/challenges were cool, the PVP is very nice.
Only problems:
- occasional minor rules infringements
- occasional bugs
- not that many players available online
- decks are pre-built.. by the way don't worry: those are 80 cards decks so you'll have the possibility to put out cards and make them better
There's also a nice bit of competition because of players charts.
I'd say it's actually the best option available to play Magic The Gathering on the internet.
The other main way, "Magic Online", surely grants access to much more cards and freedom but is graphically ugly, feels messy and costs a lot of money (you have to purchase virtual versions of any card you want to play and you can't redeem them without paying a lot on shipments and when they go out standard format they're worthless).