I think rhyming is a very difficult thing to teach ABOUT, even though it is something most kids can do. When you think about it, rhyming is about final syllables of words and how those syllables are similar in vowel-consonant combination. HUH? No wonder it is hard for some kids to "get."
I just use a lot of rhythmic verses and leave the last word blank. I hardly ever have a child who can't fill in the blank with a rhyme, but if I ask
that same child to tell me a word that rhymes with ___ they often can't tell me. Instead, I often get kids telling me words that start with the same sound -- something they do all the time in school. I think teachers underestimate how confusing that is for kids. If a child does have trouble filling in a blank with a rhyme, I can usually get them to do it by REALLY emphasizing the rhythm, tapping or clapping (or even moving and "cheerleading") to get the word out.
I think the best rhyming sources are kids books. Dr. Seuss is great. My personal favorites are Taxi Dog by Deborah and Sal Baracca and the "Bear" series by Karma Wilson (Bear Snores On, etc). I read the whole books out loud first, and then go back to find the rhyming words.