The Unsupervised and Transfer Learning Challenge is being held until April 15. The goal of the challenge is to “[...] devise preprocessing algorithms to create good data representations. The algorithms can be trained with unlabeled data only during phase 1 (unsupervised learning). Some labels (from other classes than those used for evaluation) will be made available during phase 2 (transfer learning).”
There are prizes to be gained and the first phase submissions are being accepted until February 28, 2011.