This PowerPoint is a great introduction to adding mixed numbers with unlike denominators. I used it as a minilesson my 5th graders before math workshop. During the presentation, I like to walk around the room while the students solve problems on white boards. My AP was observing me during this lesson and she loved it!
We use "chin it and spin it" when we use white boards. Students solve the problem on the board, hold it to their chest/chin (chin it) and show me after I say spin it. This allows me to easily assess who is getting it and who may need a small group after the minilesson.
I hope you enjoy!