What's working for us:
Discover and Do DVD along with the Usborne book. He LOVES it. We do experiments daily. Oh, I also have the Science kit from Sonlight, but hte materials aren't hard to come by, and you can adapt most of them (even with the kit you ahve to come up with materials for every experiment). I want to get the second DVD, but he's still loving the first one, so...
Books with science experiments... he especially has liked this one:
http://www.delmarlearning.com/browse...EA&cat2ID=EA24
The experiments are ordered by letter (A--absorption, B--birds, etc) There are several for each letter, and cover lots of areas of science. They are designed for preschoolers and are very experiential, but Erik has enjoyed every one that we've done. (I just now see on the back of the book that they also have Art activities A to Z... Cooking... Math... as well. I might check them out too).
We just got the Real Science 4 Kids prechem--it looks WONDERFUL. I am so excited to start it. It has a great textbook, and then experiments to go along with it. It also teaches a good process for thinking through the experiments. I'm glad Lisa had it for sale and I bought it--I was going to wait, but it's perfect now.
We check out science experiments books from the library every week, too. Mostly he likes to read through those, but sometimes we do experiments in them.
With planets, a huge love of his, we look at this site online a lot--http://www.nineplanets.org/ We also have many, many books about planets.