I thought this might be useful for many people. It enables you to view how a membrane protein is orientated in the membrane.
At the OPM site, you'll discover 162 proteins from over 60 species grouped according to type, class, family, superfamily, and localization site. Click on a desired protein, and you can view it in ribbon form or in 3-D relative to the membrane it resides in.
http://opm.phar.umich.edu