IXL has over 4,000 k-12th grade skills and offers unlimited practice! Fourth and fifth grade student’s typically enjoy the format of this site as the skills are very specific, and they can work on the skill sets they need more practice on.
This is a great site for students 3-8 years of age. The reading levels are from pre-k-2nd grade, and the approach is successful for those learning to read, or those moving at a slower pace due to learning difficulties.
This site is also a favorite of mine as it has reading lessons, phonics games, and tons of books for students ages 2-13!
This is a fantastic site for incremental skill building and leveled books. It allows your child to read at the level he/she is currently on.
Study Island has a myriad of skills that are aligned to each grade level. The format is similar to the STAAR exam that students are given at the end of each year.