Have traps such as arrows in the wall, swinging scythes, crushing walls and the like... the "classics". Give the party a chance to notice them... Anyone can see arrow slits or a gap for a scythe to swing.
If triggered then have it be a Skill Challenge to get through... via Balance checks or climb or tumble or just have them roll reflex. On a fail just be like "you make it through the scythes but are caught by one, slicing your thigh on your way out * appropriate damage*
On a bad roll have it do double damage.. so the DC might be 20, 10-19 = damage, less than 9 = double damage.
Have some traps detectable via detect magic, as mentioned before, then either make them easy to avoid "Walk around the trapped tile" or a jump check or similar "Jump over the trapped tiles" or by using Log the Wildnerness Rogue to trigger so you can pass through after the badness has been wasted (useless on autoresetting traps). For things like a pressure plate the party could leave a heavy rock on the plate, preventing the trap resetting, if you have pressure plates, describe the room as having some damage done to the walls and there's chunks of stone lying around... giving perceptive or attentive players a bonus option.
Also... have sneaky traps... have a door handle of bestow curse... -2 to all stats until you find someone to remove it etc. Have your traps be an actual hindrance... Every party carries around wands of vigor or cure light wounds or have a "healer" which make traps not a big deal when they just deal a bit of damage... just a HP tax... the ones that deal ability point damage or curse will make the following traps / fights harder and your players will feel the toll.
Have traps open combat. "Stepping on the floor triggers poisoned darts to shoot the party... but it also drops ooze from the ceiling. Roll Initiative". If the Darts hit or make them autohit but that raises CR of the trap, save vs poison for something... 1 Con? the party takes a bit of damage from the dart and has a lower con score now... which they will feel, even if it feels minor... have the oozes target the ones who failed save vs poison, when they hit say "The ooze does X damage, you also feel the poison in your veins strengthen 2 Con dmg." If the oozes continue to hit keep adding +1... or if you feel like an evil b*****d then double every time, 1,2,4,8... on each successful hit on the poisoned party member. The poison in this example would be "Initial 1 con, Secondary 1+X con", X being the number of times struck by an ooze in the last 10 rounds. Special - Apply this poison each time a player is struck by an ooze after being poisoned but before the secondary effect 60 seconds later, stacking con damage appropriately."
Consider the above vs "You take 15 damage from the saw blades."
"I use my wand and heal back up to full"
"We wander into the next room"
After a clever use of traps the party will feel challenged by them or smug that they bypassed them without a rogue. Either is a good outcome. Also... next time they go into a dungeon they might hire a rogue in town knowing that you're not going to dilute challenges just because they failed to bring a trapfinder
