We used Histology ImageReview on CD. It is extremely helpful! Each section (there are about 20 in total I guess) has 60-100 individual slides with a description. It not only tells what the cell type or structure is but also the function and any other pertinent information. It really helps in studying for the lecture aspect of histology in addition to the practical.
Our class used histotime, BU, and Kansas. When we broke into study groups, each person compiled a list of images into powerpoint and would label tissues, structures, etc. Essentially, it was a very accurate mock exam. My scores went from the 70's up into the 90's.