8. A computer system comprising: a processor for executing program instructions; and a memory for storing the program instructions, wherein the program instructions are program instructions for organizing a collection of electronic documents, and wherein the program instructions comprise program instructions that store in multiple dictionaries separate from and not associated with any particular one of the electronic documents, wherein the multiple dictionaries are data structures within the computer system, wherein individual ones of the multiple dictionaries correspond to one of a plurality of different subjects, wherein the entries contain a descriptive term and a subject-determining-power score corresponding to the descriptive term, wherein an individual subject-determining-power score indicates the relative strength or weakness of the corresponding descriptive term with respect to the subject of the one of the multiple dictionaries containing the entry in which the descriptive term is stored, and wherein at least some of the descriptive terms are present in two or more of the multiple dictionaries, program instructions that, responsive to requests to identify one or more of the electronic documents, wherein the requests include at least one search term descriptive of the one or more electronic documents, access the collection of electronic documents by matching the at least one search term with descriptive terms in the multiple dictionaries to determine one or more subjects of the request from subjects of one or more of the multiple dictionaries that contain the descriptive terms matching the at least one search term, and applying the subject-determining power scores to determine which of the subjects of the one or more of the multiple dictionaries that contain the descriptive terms that match the at least one search term are most applicable to the request, program instructions that rank the one or more subjects determined by the matching according to a match score computed for individual ones of the one or more subjects with respect to the at least one search term, program instructions that determine one of the at least one search term having a greatest subject-determining power score among the one or more subjects and a subject to which the greatest subject-determining power score corresponds, program instructions that collect document tags having a best match to the highest-ranking subject for which the document tags have not yet been collected, in a collected set of document tags for the request by first collecting a number of document tags having highest subject-match scores for the subject to which the greatest subject-determining power score for a first one of the at least one search term corresponds, and adding the collected number of document tags to the collected set of document tags, second collecting another number of documents having highest subject-match scores for another subject to which a next greatest subject-determining power score for another one of the at least one search term corresponds, and adding documents from the other number of documents to the collected set of documents, until a predetermined number of documents are identified, program instructions that reduce the collected set of document tags by retaining document tags collected by the first and second collecting according to their subject-match scores, and program instructions that store a representation of the collected set of document tags that identify the electronic documents in a memory of the computer system to provide the response to the request to identify the one or more electronic documents.
8. A computer system comprising: a processor for executing program instructions; and a memory for storing the program instructions, wherein the program instructions are program instructions for organizing a collection of electronic documents, and wherein the program instructions comprise program instructions that store in multiple dictionaries separate from and not associated with any particular one of the electronic documents, wherein the multiple dictionaries are data structures within the computer system, wherein individual ones of the multiple dictionaries correspond to one of a plurality of different subjects, wherein the entries contain a descriptive term and a subject-determining-power score corresponding to the descriptive term, wherein an individual subject-determining-power score indicates the relative strength or weakness of the corresponding descriptive term with respect to the subject of the one of the multiple dictionaries containing the entry in which the descriptive term is stored, and wherein at least some of the descriptive terms are present in two or more of the multiple dictionaries, program instructions that, responsive to requests to identify one or more of the electronic documents, wherein the requests include at least one search term descriptive of the one or more electronic documents, access the collection of electronic documents by matching the at least one search term with descriptive terms in the multiple dictionaries to determine one or more subjects of the request from subjects of one or more of the multiple dictionaries that contain the descriptive terms matching the at least one search term, and applying the subject-determining power scores to determine which of the subjects of the one or more of the multiple dictionaries that contain the descriptive terms that match the at least one search term are most applicable to the request, program instructions that rank the one or more subjects determined by the matching according to a match score computed for individual ones of the one or more subjects with respect to the at least one search term, program instructions that determine one of the at least one search term having a greatest subject-determining power score among the one or more subjects and a subject to which the greatest subject-determining power score corresponds, program instructions that collect document tags having a best match to the highest-ranking subject for which the document tags have not yet been collected, in a collected set of document tags for the request by first collecting a number of document tags having highest subject-match scores for the subject to which the greatest subject-determining power score for a first one of the at least one search term corresponds, and adding the collected number of document tags to the collected set of document tags, second collecting another number of documents having highest subject-match scores for another subject to which a next greatest subject-determining power score for another one of the at least one search term corresponds, and adding documents from the other number of documents to the collected set of documents, until a predetermined number of documents are identified, program instructions that reduce the collected set of document tags by retaining document tags collected by the first and second collecting according to their subject-match scores, and program instructions that store a representation of the collected set of document tags that identify the electronic documents in a memory of the computer system to provide the response to the request to identify the one or more electronic documents. 13. The computer system of claim 8 , further comprising program instructions that tag electronic documents within the collection of electronic documents, the program instructions for tagging comprising: program instructions that find terms within the electronic documents to be tagged; program instructions that match the terms with the descriptive terms within entries in the multiple dictionaries to determine a ranking of the multiple dictionaries by relative relation of their associated subjects to the content of the electronic documents to be tagged; and program instructions that store a result of the matching for subsequent retrieval when performing electronic document searches.