Zork like set of games (parchment.toolness.com)

Playing Rybread Celsius on my browser is giving me the warm fuzzies. Those were such fun times!...

I recommend Emily Short's fractured fairy tales (Bronze, Glass) and Galatea. They're all well-written and pretty well-programmed; Glass is funny and the other two are a bit trippy/strange. IIRC they all have multiple endings.

If you like Lovecraftian horror then Anchorhead is highly recommended. A really well made game and the writing captures the mood perfectly.