Hints for Maniac Mansion -- These hints by Kevin Carnes will get you through the game and help you solve the puzzles on your own.
Howard & Nester do Maniac Mansion -- A regular feature in Nintendo Power magazine, Howard & Nester was a comic strip about two game whizzes who would one-up each other, while disclosing hints and tips, in the settings of various recently-released games for the NES platform. In Volume 18's two-page installment, they explore Maniac Mansion with Razor, encountering Dead Cousin Fred, Green Tentacle, and Nurse Edna (the blue-skinned one, of course, from Jaleco's NES release.)
LucasArts' Secret History -- A multi-article feature about the game by the LucasArts news site, The International House of Mojo. The feature article includes an unscored review, short responses written by members of the site's community, trivia, easter eggs and other small details in the game, commentary from the developers, a transcription of the original hint book, a long feature article by one of the programmers, and an interview with one of the project leaders.
ManiacMansionFan's complete Maniac Mansion reference page -- A complete and extensive website about Maniac Mansion
ScummVM -- A useful program for playing old SCUMM games on newer operating systems (for example, Win XP).
The Expurgation of Maniac Mansion for the Nintendo Entertainment System -- an article about the censorship and the revisions the NES version of the game was forced to go through
The Maniac Mansion Fan Site -- Site that gives info on all versions of Maniac Mansion.