Hi,
 
When I've taught cause and effect, I've taught it from my student's own experiences, whatever their age level.
 
For example, if you're teaching kindergarten and grade one, you could draw cause and effect pictures, with the planting of seeds on the left side of a page, and then a plant growing on the right side of the page.  Or you could have the students draw a sequence of pictures from left to right, showing the progress from a planted seed (getting water and sunlight) to a green leafy plant.
 
There are many experiences in a young child's life that you could use to develop this concept, e.g. the growing of their pets, their own growing, having injuries and bandaging them, being nice to people and having friends, etc.  The possibilities are numerous for doing cause and effect at this young age.
 
You could use the curriculum at each grade level to develop cause and effect topics.  By high school, students are looking at causes and effects with topics like war, poverty, education, forms of government, etc.  
 
If something is too abstract for your students, at whatever grade, then we need to show them how that topic is related to their own experience.  For example,  if national government is being taught, and cause and effect questions are being asked, then I would first talk about "government" in their own home, asking questions like:  Does anyone make rules in your house?  What kind of rules do they make?  Does everyone obey those rules?  Should everyone obey those rules?  Do you make rules in your house?  Should you be able to make rules in your house?  Should everyone obey the rules you make?  There are many cause and effect examples that can be developed from any of these questions.  
 
Gradually, we need to move students from their understanding of familiar, concrete experiences, to more abstract, unfamiliar concepts.  Whatever the topic.
 
I haven't really talked about worksheets or pre-prepared materials.  I think we can develop cause and effect materials with our students.  The only things that will be different are the age of the students and the curriculum requirements.  We can get examples from their own experiences, from the books they read, and from curriculum textbooks.