While many others have done this project, I worked at optimizing the view angles and publishing these. CD Spectrograph in a Box is a simple educational one evening project. Everything you need to know should be evident in this one photo, but following steps give space for commentary. Note: a spectroscope is to view spectra, a spectrograph is a recorded image (photo) from a spectroscope, a spectrometer measures spectral wavelengths.
Check out DoWatts DVD Spectra instructable.

Step 1: Supplies

*Masking tape or duct tape. Duct tape is better to keep light out from cracks. Otherwise,use a black felt marker on tape to keep all stray light out of box.

*Single edge rasors or a breakable thin rasor blade work well. For a children's safety version, use the opposite edges of a credit card cut in half. It will save you a lot of money!

*The LED's are fun to observe as is a compact flourescent light. The laser pointer is dangerous and should be used with care and only to illuminate a translucent plastic bag covering the slit.

Any CD that you don't mind damaging

Step 2: Construction

Glue a cardboard plate 70mm from the top and keep it horizontal, Especially from side to side! This is just to support the CD which you may hot glue or tape in place. If you place the plate lower than the recommended 70 mm, the CD must be a little farther from the far edge of the box and the viewing hole must be proportionalely farther from the front edge. Try to keep the angles correct. The incident angle is about 13 degrees from perpendicular and the viewed angle is about 47 degrees from perpendicular or 43 degrees from the horizontal. Note that the angle of the diffracted light is NOT the same as the angle of the source (incident)light.
A hole 10 mm x 20 mm is cut far enough from the front edge to allow taping two razor blades in place 1 mm apart or less. A viewing hole 25mm square is cut 95 mm from the slit. This hole can be slightly oversize for ease of viewing. The light guard is not essential but it is definitely helpful. Hot glue was used in much of the construction. Again, it is not essential but made things easier.

Step 3: Cereal Box

Cut slits in the box to support the CD. The slits must be placed identically on each side of the box. CD slits should be 1 mm to allow space for the CD to slip in without distortion. CD slits are 70 mm down from top of the box. Illumination slit is 15 mm from front edge. Viewing opening is centered 95 mm from the illumination slit.

I welcome links to similar projects to be posted here.