This week, my class will be working on Compound Sentences.  I have made a complete unit, with a test and all for my class.  You can find it here:  http://www.teacherspayteachers.com/Product/Compound-Sentence-Unit.
I am using it with my third graders, but it can definitely be used with fourth or even fifth graders.  I'm sure it can be adapted for second graders as well!  :)
Here are some pictures of what is included in the lesson.

 These cute little train cars are used to create compound sentences.  Students will write a simple sentence on a "topic train car", and pair it with another student's simple sentence using the same topic.  They will then choose the correct conjunction to put between the sentence.

This is part of the test that can be given at the end of the unit. in the unit.

There is also a PowerPoint presentation to be used at the beginning of the lesson, including a review of simple sentences, and subject and predicates; and also a fun foldable to remember the conjunctions.

And of course, who doesn't love SchoolHouse Rock?!?!?  I usually play this clip for my kids too.  :)http://www.youtube.com/watch?v=ODGA7ssL-6g  They always love it!  :)