When introducing the major triads I like to use some food analogies to help my students remember what they look like on the keys.
"The Vanillas" are C, G & F - all white keys, like a triple decker vanilla cone
"The Hamburgers" are D, A & E - white on the outside and black in the middle, like a hamburger
"The Oreos" are E-flat, A-flat & D-flat - black on the outside and white in the middle, like an oreo
"The Oddballs" B, B-flat & F# are just odd, they don't fit in with any of the other triads
For a group lesson I had my students cut & paste small pictures of ice cream cones, hamburgers, oreos and draw their own oddballs on a Circle of 5ths chart. They especially enjoyed designing their own oddballs:). I find this activity especially helpful for students who are visual learners. A few times I've even rewarded the students at the end of their lesson with an oreo when they can play all of their "oreo triads."