Spinnaker is most well-known for their excellent educational games such as Snooper Troops and In Search of the Most amazing Thing. These games were used in many schools and made learning fun. They were also responsible for a number of other well-known labels

The Telarium label is unique in that all of their stories were based on published novels by respected science fiction, fantasy or mystery authors. The games typically came in flat folder-like packages, though some later releases came in normal boxes as well. Most were text adventures, though Shadowkeep is as much of an RPG as you could get.

The Windham classics were a series of games produced by Mindscape (I think) based on classic novels of recent time.  All did a good job of reproducing the stories they were based on.  While most were graphical adventures, Alice in Wonderland and Below the Root were far more complex action/adventures, with lots of interactive puzzles and interesting characters.  These are two of my all-time favorite adventure games, and few have come close to them in sheer size or quality since (IMHO).