The resources described here are designed to help 5th grade students and their teachers explore some topics related to measurement and geometry, namely: finding and differentiating among perimeter, area, and volume, and measurement of right, acute, obtuse, and straight angles. There’s lots of great stuff out there, and I hope these resources will be helpful!
Fantastic Books:
Sir Cumference and the Great Knight of Angleland by Cindy Neuschwander, illustrated by Wane Geehan.This charming book follows the adventures of Radius, son of Sir Cumference and Lady Di of Ameter on his first quest to rescue the King of Lell. In order to rescue the King, Radius must use his trust family medallion – which looks suspiciously like a protractor – to solve a maze of many angles. A wonderful introduction to angles and how to measure them. There’s even a replica of Radius’ medallion in the back of the book. 
What’s Your Angle, Pythagoras? by Julie Ellis, illustrated by Phyllis Hornung. This fictionalized history follows the famous mathematician as a young boy as he discovers his famous theorum on a trip to Alexandria with his merchant father. It’s a fun introduction to the unique features of the right triangle, with rich, whimsical illustrations that really enhance the journey. A great way to begin exploring angles and triangles.
Spaghetti and Meatballs for All! by Marilyn Burns, illustrated by Gordon Silveria. Mr. and Mrs. Comfort are planning a big family dinner. The food is ready and the tables are set – 8 tables, to be precise, with 32 chairs. But as the guests arrive, they begin to change the seating plan and chaos ensues! This book is a fun way to get kids thinking about perimeter and area.
Racing Around by Stuart J. Murphy, illustrated by Mike Reed. This book may be a little juvenile for many fifth graders, but it remains an excellent introduction to the concept and measurement of perimeter, while making a strong real-world case for why this math matters.
Millions to Measure by David M. Schwarz, illustrated by Steven Kellogg. Kids often understand a topic better if they know its history. This book traces the development of standard units of measure for distance, weight, volume, and more, going on to detail the development of the metric system. A fun and brightly illustrated melding of history and math.
Web Sites for Kids:
Here are some sites that are great for encouraging kids to explore measurement of angles and perimeter, area, and volume on their own. These are all interactive and engaging, and provide some wonderful opportunities for kids to lead their own learning.
"Measuring Angles" – Interactive practice for kids learning about how to measure angles. Kids drag a protractor over a specified angle in a random polygon and select the correct measurement.
"Everything About Area and Perimeter" – Interactive game in which children find the perimeter or area of a shape. There are three levels, and at the most complex, kids are asked to find the perimeter or area of a compound shape. Step-by-step instructions break the process into easily manageable steps.
"Shape Explorer" – Students explore the relationship between area and perimeter, and are able to keep a running record of their findings. This site allows for varying levels of expertise. Beginners can restrict the shapes to rectangular arrays, while more experienced students can expand the size of more unusual shapes.
"Finding Volume" – Kids watch as rectangular prisms are constructed by the computer, then calculate the volume of the resulting figure. Comes with a printable recording sheet to expand student learning.
"Angle Invasion!" – Alien spaceships are invading, and you have to save the world! Kids estimate angles between 0 and 180 degrees in 10-degree increments to shoot a laser and blow up the invader – 3 strikes and game over. A fun way to hone kids' sense of angles and their ability to estimate outside the "easy" angles.
Additional Resources:
These resources are some good, general supports for instruction in measuring angles and perimeter, area, and volume.
"What's My Angle?" – A set of 10 online activities that support the teaching and investigation of angles, as well as an introduction to relevant vocabulary. Includes activities ranging from estimating to specific measurement, and is kid friendly enough to make an independent activity.
"Electronic Geoboard" – This site can be used in conjunction with the "Building a Clubhouse" lesson provided in the print component. Alternately, this is a great way to demonstrate how to use a geoboard to find perimeter and area. Kids can explore further electronically to reinforce their hands-on classroom discoveries.
“Geometry Festival” – This is a link to a week’s worth of activities about area and perimeter, based on Marilyn Burns’ “Spaghetti and Meatballs for All” and Cynthia Rylant’s “The Relatives Came.” The layout is a bit dense, but the activities are nice and detailed, and there are ideas included for extensions and for assessments.
“Geometry Bingo” – Help students review geometry terms with this fun bingo game! This is a printable PDF that includes game boards and calling cards.
“Rules and Practice with Angles” – Practice with measuring angles and types of angles (acute, obtuse, right, and straight). This is a free printable PDF. It includes all the relevant answer keys.