We've used TOPS science modules ( www.topscience.org )a few times here--I'm of two (or some number!) minds about them, I think, but they are both secular and inexpensive. Most of the supplies are "homemade", and while I appreciate both the ingenuity and the philosophy behind that decision, we found some of the equipment frustrating to use. My bairns are still pretty wee, though, so it may have been more a fine-motor thingy than something inherent in the materials.

Somebody here (incogneato, I think) likes Bite-Size Physics ( www.bitesizephysics.com ), which I am pondering. It looks really fun!

peace
minnie