This set of warmups is great for review of the 8th grade Common Core standards each day. I have these waiting on the students' desks when they come in, and after a set amount of time we go over the answers together, usually with several students taking turns doing the warmup under the doc cam. Depending on the pacing of the day, I may have students complete only two of the problems, or even just one if it is a complex problem.
This set has 25 warmups with accompanying answer keys. Along with linear functions, the concept of identifying functions from any set of relations is also covered.
I really strive for mastery of a topic, so my warmups cycle back through previous concepts in the unit to keep my students constantly reviewing. As we move through the units, I will often go back to warmups from earlier units to ensure students are maintaining those earlier concepts as well.