Anyone working in physics knows that Physical Review Letters (PRL) is one of the most prestigious journals to get published in. In fact, in high energy physics, it is THE most prestigious journal to published in (since I it appears that high energy physicists, especially experimentalists, seem to have an unofficial "boycott" of Nature and Science).
In any case, PRL will turn 50 this year (2008). So you can expect them doing a few special things to mark this occasion. One of the things they are doing already is to highlight some of the important, milestone papers from the past. "Letters from the Past - A PRL Retrospective" lists papers that have made significant impacts, even some time winning the author a Nobel Prize. The best part about this is that you can access these papers for free. More papers will be added to the list, so check back regularly.
So while the actual date is still a ways away, let me send out my early wish and say "Happy Birthday, PRL!"