RAZ Kids
Great for online reading, listening to books, and reading activities.

IXL
An amazing resource for ALL of our math learning this year!
Addition, Subtraction, and Place Value
Fractions Practice 
Includes, length, capacity, and weight
Math Fact Cafe
A great resource for students to practice facts (+ and -). Also provides online flashcards.
Nature Works
Great information on nature and the environment.
Soil Science Society
Includes some fun at home projects - including how to make edible dirt!
Inside the White House
An interactive tour inside the White House.
Mr. Donn
I'm not sure who Mr. Donn is, but this site has great links!