Pythagorean Theorem
This interactive site will help you verify that the sum of the squares on the legs of a right triangle equal the area of the square built on the larger side. It is a fun site which may enjoy.
http://www.ies.co.jp/math/java/samples/pytha2.html

Similar Triangles
An example of similar triangles is given at this site.
http://www.vcsun.org/~bsamii/schedule/notes/geo/Similarity/similarity.html

Introduction to the words "sine", "cosine", and "tangent", as well as some practice with these trigonometric ratios. Links to some applications are also provided.
http://regentsprep.org/Regents/math/rtritrig/Ltrig.htm