The other day I set out to find science sites in English and Spanish that offered lesson plans, experiments, or were otherwise child-friendly. You can't imagine how delighted I was to find that someone had already done my homework for me! I had thought to begin a long list of sites here, but instead I have just a few that have already done the research and that present links to sites in an organized manner. Enjoy!
TRABAJOS PRÁCTICOS Y EXPERIENCIAS DE LABORATORIO - This first site is perhaps the best site out there for bilingual science resources. It lists around 149 sites from around the world in both English and Spanish. This should be your go-to source.
Ciencia para chicos may be my next favorite. It also lists sites in both English and Spanish, and though there is some overlap, they are for the most part different links.
ABChicos.com lists a variety of sites, though not quite as comprehensive as those mentioned above. I have not gone through all of them, but I think they are Spanish-only sites.
TryScience is an American site out of NY that has published a website in a variety of languages including English and Spanish. I like this one, too.
This is a short list, but believe me, these few links will provide you with a wealth of information!
Con mucho cariño...