The VLFeat MATLAB toolbox provides implementations of common computer vision algorithms (HOG, SIFT, dense SIFT, MSER, AIB, KMEANS, learning large scale SVMs...) and many utility functions (e.g. precision-recall, ROC, DET curve calculation, plotting functions). To get started:
Type vl_help doc
Type vl_help online
Use the help command to get information about any VLFeat function
Directly check the documentation online: http://www.vlfeat.org