Legends of Zork is basically a graphical, browser based MUD, or multi-user dungeon, with some distinctive Zork flair thrown in for good measure. You're an out of work salesperson for FrobozzCo International who ventures out into the wilds to earn fame and fortune hunting monsters, solving puzzles, or defeating your fellow players in the arena. It's got a simple yet addictive sort of gameplay, which is compounded by the fact that you can play it in any web browser, including the Safari on your iPod Touch, not that I just spent 10 minutes playing in the bathroom or anything.
Just beware. You start off with a set amount of action points per day, which are used to fight and explore, and once you run out your only option is to buy more using real currency. See, that's where they get you. With any game of this sort, you want to just take it easy, make it a part of your daily routine, and do your best to avoid falling into the extra points trap, lest you be eaten by a grue.
Legends of Zork [Official Website]