Some free websites that I find useful with my students are:
Reading:
For beginning reading skills Reading Bear is a resource that approaches reading phonetically and begins at a very basic level, with letter sounds.
StoryWeaver allows children to hear books in both English and other languages. Text levels are not very challenging, so it's better for younger students or beginning readers.
Math:
To work on specific lessons and skills, Splash Math allows some free accounts for teacher's to tailor and assign tasks.
Videos & Lessons:
Khan Academy gives lessons on a multitude of topics.
TeacherTube gives students the advantage of watching a video of a teacher teaching lessons and is searchable by content.
Bilingual Kidspot has a variety of poetry, nursery rhymes, and videos in different languages for kids to interact with.
