One common example is listo. When used with ser, it typically refers to being clever or intelligent: El mono es listo, flexible e innovador. (The monkey is clever, flexible and innovative.) But when used with estar, it often means "ready": Dice que no está lista para convertirse en madre. (She says she isn't ready to become a mother.)
One reason for the change in meaning is because ser is typically (although there are exceptions) used with enduring or innate qualities — and in the case of listo, you might think of "clever" as similar in meaning the idea of "always ready."
Following are some other adjectives that you can think of as changing in meaning depending on which form of "to be" they are used with. Important note, especially for beginners in learning Spanish: As always, context is essential to correctly understanding what is said. The "rules" here may be more flexible in real life than the way they are presented here. Also, the meanings given below aren't the only possible ones for the adjectives, nor the translations given the only possible ones.
ser aburrido (to be boring): ¿Quién dijo que la ciencia era aburrida? Who said science was boring?
estar aburrido (to be bored): Recién llegué a este país con mis padres al principio estaba aburrida. I recently arrived in this country with my parents, and at first I was bored.
ser bueno (to be good): Escuchar ópera es bueno para el corazón. Listening to opera is good for the heart.
estar bueno (to be tasty, fresh, sexually attractive): Si haces una ensalada con lechuga está buena, pero si le pones pepino y un buen aliño, ¿no está mejor? If you make a salad with lettuce it is tasty, but if you put pepper and a good dressing, isn't it better?
ser cansado (to be boring, tiresome, tiring): Buscar trabajo es cansado cuando te llenas de ansiedad. Looking for work is tiring when you are full of anxiety.
estar cansado (to be tired): Estaban cansados de la situación en su país. They were tired of the situation in their country.
ser despierto (to be sharp, alert): Los dos eran despiertos pero nadie hablaba. The two were alert but nobody spoke.
estar despierto (to be awake): Los dos estaban despiertos y podían comunicarse. The two were awake and could communicate with each other.
ser enfermo (to be sickly, an invalid): El perro llegó a ser enfermo y murió. The dog became sickly and died.
estar enfermo (to be sick): Desde hace un año, yo estaba enferma de estómago. Since a year ago I have had a stomach illness.
ser interesado (selfish): Creen que el hijo de Lupillo es interesado y materialista. They think
Lupillo's son is selfish and materialistic.
estar interesado (to be interested): Rusia está interesada en las reservas de litio que tiene Bolivia. Russia is interested in the lithium reserves that Bolivia has.
ser malo (to be bad): Siempre nos han dicho que automedicarse es malo. We have always been told that self-medicating is bad.
estar malo (to be ill, to be in bad shape): Parece que el disco duro está malo. It appears that my hard disk is in bad shape.
ser seguro (to be safe): Es seguro tomar taxi en Ciudad de Mexico. It is safe to take a taxi in Mexico City.
estar seguro (to be certain): No está seguro de lo periódicos o revistas que ha leído. She isn't certain of the newspapers or magazines that she has read.
