My mathematicians spent time this year measuring up one side of my classroom and down the other...literally. I love the following idea that I borrowed from Van de Walle. The kids used large footprints to measure my class from one wall to the other. It's a great way to work on no gaps and overlaps while using units, as well as the importance of choosing the right unit for the job.
The kids also used the following sheet for the task. The first group of students wrote their measurement in the top box. All other groups after them would measure the room and then either sign their names in the agree column or sign the disagree column along with the measurement they got.
(Click the picture for your own copy.)
I borrowed this sheet from Math Their Way and spruced it up a bit. I've used it for all types of math activities, from place value to counting to measurement to addition or subtraction (and much much more). Feel free to get yourself a copy and let me know how you end up using it too!