Hi Bryan,
The colon might be employed to condense your example. Let’s say your sentence came from the following text. "Mary Poppins carries a magic portmanteau of her favorite things. Among these are soap, water, and computer chips". Now let's use the colon. "Mary Poppins carries a magic portmanteau of her favorite things: soap, water, and computer chips." The problem with this last construction is that it loses the notion conveyed by “among” that the things listed are only a partial contents of the bag. Care is advised: no one ever said this stuff was easy.
Many desk dictionaries have a style or grammar section. If you turn to page 1535 of Merriam-Webster's 10th Collegiate, you will see no less than eight acceptable uses for the colon. If you don't have a copy of MW10, you are not using the favorite of the true linguaphile. Not all dictionaries are created equal, and I would further aver that no other desk-sized dictionary is equal to the Merriam. I'll spare you the reasons, since you doubtless have no desire to hear more about the descriptivists, citation files, language research, and the like. Suffice it to say, if you harbor a true desire to understand and emulate the language of your fellow native speakers as it is spoken today, you will appreciate this dictionary. Besides, all those permanent language scholars and lexicographers at Merriam are depending on sales to put their kids through college. I always like to be helpful. :-)
--Jeff