www.sparklebox.co.uk (K-2) Tons of resources adding, subtracting, basic multiplication.
www.songsforteaching.com Includes lyrics for lots of math concepts.
www.k-5mathteachingresources.com work stations, activities, and some literature with a task card to go with it.
www.multiplication.com free to sign up and enroll your students.
www.xtramath.org math facts and activities.
http://www.thinkthroughmath.com/ math practice with all concepts.
www.bigbrainz.com, Requires a download in the computer to work.