Khan Academy
Instructional videos and practice exercises.

IXL Learning
Educational practice for K-12th graders in MATH, Language Arts, Science, Social Studies, and Spanish.  IXL provides step by step instructions and solutions after incorrectly answering a practice problem. 

VIDEOS
Finding x- and y-intercepts on the Calculator, TI83 & TI84 (00:00-3:10)
Linear Regression and Correlation (09:05)