When I began setting up this station in my classroom 5 years ago, I actually started by posting a project on Donorschoose to get hands-on science activities (for more info on Donorschoose, read this post)!
After brainstorming my topics (1 for each month), I went shopping online on Nasco, Lakeshore, and Kaplan for any hands-on activities related to my topics. I also asked for general science materials like scales, measuring tapes, calculators, and general science file folder activities to be used year-round. Then, as I waited for my projects to be funded (which they were!), I started creating my own worksheets and activities.
I definitely recommend using Donorschoose to supplement your science units. Unfortunately, since I wrote these projects about 5 years ago, a lot of the materials are no longer available. Here are some of the items I found still available:
Inflatable Solar System (for your solar system unit). We hang this in my classroom every year and the kids love it!