How to make transparency effects?

How would I go about making the material/texture for an object such as a wine glass? I found the alpha option for MapTo in the texture panel, but I can’t get it to work for some reason.

http://img228.imageshack.us/img228/9346/savoywineglasswb0.jpg

There are several ways to achieve transparency. http://feeblemind.tuxfamily.org/dotclear/index.php/2004/12/26/7-didacticiel-la-refraction---tutorial-refraction
It shows how to achieve the effect with raytracing and refraction. This would apply to the wine glass. If you want an object to simply be half or some other percent visible, you can use the alpha channel, located underneath the color sliders. When renderering with raytracing, remember to turn on the ray tracing mode.

Cool, works nicely. I like the IOR chart that site has.
Thanks for the quick reply!