ClassFlow
Class Flow: Parallel Lines and Planes
[Free Registration/Login Required] This flipchart defines parallel lines and planes. It defines a transversal, the concept of alternate angles, and vertical angles.
Shmoop University
Shmoop: Basic Geometry: Basic Shapes & Angles
The geometry resource explores basic shapes, lines, and angles. Descriptions, examples, and practice problems are included.
Shmoop University
Shmoop: Basic Geometry: Parallel Lines & Transversals
The geometry resource explores parallel lines and transversals. Descriptions, examples, and practice exercises are included.
City University of New York
Lehman College: An Introduction to Lines
Use this site for two short lesson plans regarding Euclidean and Spherical lines. Intersecting and parallel lines are discussed. The lesson contains activities for two days of class.
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Perpendicular and Parallel Lines
Find a quick, concise explanation of what perpendicular lines are. An example is given and clearly explained. Also, parallel lines are explained.
University of Georgia
University of Georgia: Inter Math: Perpendicular Lines
This site from InterMath opens with a very simple definition of perpendicular lines and has links to challenging problems, more information, related terms and everyday examples of perpendicular lines.