Learner.org is a fantastic site with loads of different projects about nature, cycles of the moon, the seasons and more. I've linked their Monarch Butterfly Migration project and information here. The project has several components to take part in, including a paper butterfly migration option. Although the paper butterfly migration is meant for school groups, I would imagine that a homeschool group or co-op might be able to take part.
National Geographic Kids is a wonderful site with factual information, pictures, videos,and more. We used it when my son was in 4th and 5th grades, and we learned about animals from around the world.
This video starts with flamingos, but also covers butterflies in swarms. The video discusses the advantages of swarming behavior. Please note, there is a joke about a singles bar. Thought I should let you know just in case you watch and the kiddies ask what that is.... If you scroll to about 1:35, you can watch just the Monarch portion.
National Geographic Monarch butterfly coloring page HERE.
Monarch butterfly life cycle coloring page HERE.
Multiple coloring pages HERE.
Lifecycle of the Monarch butterfly from the Chicago Nature Museum. This is a time lapse video with music and subtitles but no actual audio narration.
Monarch Watch has more great info about Monarch butterflies, as well as information about determining gender, about parasite effects on Monarch populations, tracking, and tagging.