1. A computer-implemented method comprising: determining, for a current question presented by an asking user and for a plurality of existing questions within a plurality of online communities that each has a plurality of users contributing answers to the plurality of existing questions, a plurality of question-to-question similarity values; determining, for the current question presented by the asking user and of the plurality of users contributing answers, a plurality of question-to-user similarity values; determining, for the current question presented by the asking user and the plurality of online communities, a plurality of question-to-community similarity values; selecting one or more of the plurality of online communities based on the plurality of question-to-question similarity values, the plurality of question-to-user similarity values and the plurality of question-to-community similarity values; and routing the current question presented by the asking user to the selected one or more of the plurality of online communities.