This peer-reviewed online journal has been infrequently published since 2001, providing an interdisciplinary platform for research on game research.
More than any other games research journal currently in publication, Game Studies (as the journal is commonly known), brings together an international authorship, pulling many articles from researchers in Western Europe as well as the United States.
The most current issue is from August 2007, featuring a mix of articles regarding the aesthetics of games, cooperation in multiplayer games, narratives in games, and content analysis. If you think that hacking and slashing is all that there is to computer games, check out this journal for an eye-opening look at ludology.