Despite astronomy’s widespread inclusion in curricula prior to the 20th century, educational research in astronomy is a relatively new endeavor. To date there are no dedicated paper journals for astronomy education research, although the electronic Astronomy Education Review (http://aer.noao.edu) has recently released its first issue. As the field of astronomy education research grows, many may find it useful to know what has been done so far. The new SABER database represents an ongoing, collaborative attempt for the astronomy education community to collect and summarize the highly dispersed literature on astronomy education research, although it is not yet complete. Starting with and expanding beyond this database, a systematic review and classification of the literature was performed. Some of the research themes that emerged include: student beliefs and misconceptions; collaborative learning; and the Astronomy Diagnostic Test. Key studies in these areas are described and a bibliography is presented.