All 2-dimensionalThe classification of associative algebras over any field have been classified. There are manyin low dimensions has a long referenceshistory, beginning with the classificationwork of Peirce. ForA good survey, and a modern treatment see for example http://arxiv.org/pdf/1205.1221.pdf.classification of There are two cases: characteristic twoall nilpotent associative algebras of low dimension, andover an arbitrary field, also of characteristic different from twotwo, can be found in the paper of W. Implicitly such equivalence relations are treated de Graaf, toosee http://arxiv.org/abs/1009.5339. I do not know if an "explicit list" of representatives is possible for the general case.