Computing the Values of Trigonometric Functions of Acute Angles

The University of Idaho provides an online resource.  These lectures are only viewable by those with DSL or cable modems.  Real Player, a free download, is required to see these videos.
The 45-45-90 right triangle
The 30-60-90 and 60-30-90 right triangles
Similar Triangles
Finding the missing sides of the special right triangles

Non-video resources:
The 45-45-90 right triangle
The 30-60-90 right triangle
The 45-45-90 on TheMathPage.com
The 30-60-90 on TheMathPage.com

Watch the lesson on mathtv.com, but skip the second problem. Click the play button in the lower left corner of the video lesson screen.  It requires Real Player, a free download. A couple of word problems are solved in this second video, but skip the first problem.

Problems 3-6 on this page are helpful.
Example 2 on TheMathPage.com deals with an angle of depression.