Journey to the Center of the Earth

Frogwares: Journey to the Center of the Earth - http://www.frogwares.com/journey/
Official site contains screenshot gallery, demo, and links.

Game Boomers Walkthrough - http://www.gameboomers.com/wtcheats/pcJj/Journey.htm
Detailed walkthrough page with screenshots of puzzle solutions.

Low-Spoiler Guide to Journey to the Center of the Earth - http://www.angelfire.com/hero/tjekanefir/center.htm
Review, gameplay hints, and walkthrough with spoilers on a separate page.

Universal Hint System - http://www.uhs-hints.com/uhsweb/jttcote.php
Click-through hints revealing progressively more information about the game.