In Search of Software

I forgot to mention I am in search of quality science and reading software that will meet a wide range of grade levels. I am looking for engaging software that allows the students to practice important skills and help them develop. I am wondering if any of you are currently using a system that you would reccomend for elementary students K-8 or just K-5. I am fond of online based programs so that the students can practice at home as well but I am open to any and all suggestions at this point.