Mahout currently has
Collaborative Filtering
User and Item based recommenders
K-Means, Fuzzy K-Means clustering
Mean Shift clustering
Dirichlet process clustering
Latent Dirichlet Allocation
Singular value decomposition
Parallel Frequent Pattern mining
Complementary Naive Bayes classifier
Random forest decision tree based classifier
High performance java collections (previously colt collections)
A vibrant community
and many more cool stuff to come by this summer thanks to Google summer of code
I'm interested in machine learning techniques (graphical models, kernel methods) applied to text understanding (entity and relation extraction, coreference resolution, document classification and clustering, confidence prediction, social network analysis, data mining).
P. Cimiano, J. Völker, and R. Studer. Information, Wissenschaft und Praxis, 57 (6-7):
315-320(October 2006)see the special issue for more contributions related to the Semantic Web.
K. Liu, B. Fang, and W. Zhang. Proceedings of the 19th ACM International Conference on Information and Knowledge Management, page 1109--1118. New York, NY, USA, ACM, (2010)