Memes have recently come into vogue in the context of 'viral' transmission of basic information units in online social networks. However, from their original general definition in a sociological context, there is still much work to be done from an information technology viewpoint. This includes such issues as how to process memes from real text corpus, formal definitions for knowledge representation, meme refinement and selection. In order to address these issues, in this paper we adapt definitions from the semantic network and information retrieval fields to extract memes as semantic networks from free text documents, and then we present some examples in the context of a simple online forum.