[pigscantfly]

In the case of vision, there were a lot of things going on, but support vector machines, sliding window search, descriptors with invariances to different transforms like SIFT and HOG, spatial pyramids, deformable parts models, and mixtures of gaussians are all hot topics that you'll regularly see in papers from the early 2000's. There was a lot of work on improving runtime for these techniques going on, since training SVM experts and evaluating anything over a sliding window search space is very expensive. You'll also see a lot of work on approaches rooted in graph theory like conditional random fields, different flavors of Markov models, min-cut/max-flow based algorithms, and other types of probabilistic graphical models. Most of this stuff is still in widespread use; AI is a big field.