Just go here:
http://www.xs4all.nl/~pot/infocom/While these were juuuust a bit before my time (I cut my teeth on Kings Quest/Space Quest), I nevertheless played the heck out of them, and to this day they still present a HUGE challenge. Not a hyper-caffeinated twitch challenge, but one that requires the ol' noodle...and that something that will never get old!
For the new guys, try "Zork" first and see how it goes...my favorite remains "Planetfall", though!
