I played Shade by Andrew Plotkin a few years back, and then learned that he also wrote a Macintosh game I played as a kid called Systems Twilight. Speaking of which, the modern IF writers have a secret hangout called ifMUD. It's a sandbox MUD that anyone can edit, and if you go on there you might meet the people who made some of your favorite games. I was able to talk to Plotkin on there.
Inspired by ifMUD, I wrote Dennis, a similar experience which is hosted at http://dream.uboachan.net/
if anyone's interested. If you learn the commands you can expand the world, but it doesn't have a ton of features. It does have a ton of content so far though because a lot of people played on there.
I played a few of Plotkin's other games, and those are all pretty great. I played some Zork and didn't finish it, and dabbled in a bunch of others. There was another much older game that I can't find anymore that I really liked and I'm still searching for it, but I'm worried it's not hosted anywhere anymore because Google isn't producing it from keywords that should work. :(