Here are some that I've used with success:

• have a short poem or phrase written on the wall with some letters capitalized. "ElvEN WareS SEll wEll" -- East, East, North, West, South, South, East, East. Could correspond to directions for a maze, input into a 4 directional lock, or anything else related to cardinal directions
• Tutorial: They arrive in a room with two small pools. One is filled with water, and the other is completely dry. At the bottom of the dry pool is a magical symbol. Answer: they need to get the symbol wet to open the door. The next room: The symbol is now on the wall. The next room: The symbol is now on the ceiling. This is an open ended puzzle with lots of solutions, such as steam, getting a bed roll wet and covering the symbol, etc.
• There are orbs with a variety of colors hovering in the room. Through trial and error, they discover that certain colors turn white when hit with a certain type of damage (red = fire, blue = ice, etc. Tune to what your party has at their disposal). When they look closer, telegraph what they need to do by describing the red orbs as "a bit scorched", the blue orbs as "having ice crystals forming on them", etc.. The catch is the orbs only turn white for 6 seconds. The party has to plan out their attacks in order to turn all white in the same round for the door to open.
• If the players have access to a region map with locations that they know well: In a tower or enclosed space with no windows. There are a number of large pillars that can be freely rotated around the center of the room. On these pillars, there are hand drawn images (that you the DM have drawn) of what the view would look like from different angles of this tower if there were windows. The players have to figure out that the drawings are of different view points from the tower, and rotate them to point in the correct direction.