Measuring Penny is a great book to read that teaches many equivalencies. Then, we bring in stuffed animals to measure their arms, legs,head, etc.

Students eat a Twizzler in 12 bites to remember 12 inches equals one foot.

Take a length of yarn. Let students hold both ends. Fold it in half like you're folding a sheet. Tie another color of yarn like a flag where the fold is. Fold again. Tie flags. When it is opened up, the flag's mark 1/4, 1/2, and 3/4.

I am working on a measurement unit, too. If you search the proteacher site for "measurement", you will find many ideas. I also got the book mentioned by clanna Measuring Penny. I look forward to having students bring in a stuffed animal and measuring their parts. Thanks clanna!

I also like the idea of having students go on a scavenger hunt outside looking for items with a specific measurement:
Find an object that measure exactly one foot.
Find an object that is less than 10 inches.
They enjoy this activity!

Another book you can use is The Queen's Bed or How Big is a Foot? I have seen it under both titles. It demonstrates the need for standard units of measurement when an apprentice has to make a bed for the queen using his feet to measure. Of course, the bed wouldn't fit the queen.

I like your idea of going outside for a scavenger hunt. This is the way it is usually presented on our state test ---Which item is about 10 inches?

A mini Olympics is GREAT for all sorts of measurement. Here is a unit, an oldie but a goodie, that you could adapt/update. I have done these activities with Gr 3&4. when we held a mini Olympics. We set up stations (indoors is ideal if you have a large enough hall/ space), the children were divided into groups , each with a captain, and then they rotated through all 6 activities. The events finished with a scavenger hunt. It was great fun as well as terrific measuring practice.

Last year when we studied measurement I paired the students with a partner and using a tape measure they measured each others arm length, arm span, head, tracing of their foot, waist, and height. It was a great cooperative hands-on activity. Then we used the information to create a chart of the largest and smallest of each measurement. You can even graph the results of any of the measurements.