Unsupervised learning does not require annotation or labeling from a human teacher; the idea is to learn the structure of the data from unlabeled examples. The most common unsupervised learning task is clustering, i.e. grouping instances into a discovered set of categories containing similar instances. Self-organizing maps in addition visualize the topology of the clusters on a map. Our work in this area includes applications on lexical semantics, topic modeling, and discovering latent class models, as well as methods for laterally connected, hierarchical, sequential-input, and growing self-organizing maps.