The ArXiv is a popular pre-print article server for physics, mathematics, and computer science (and other subjects) hosted by Cornell University. It is a fairly common practice for academics to upload a preliminary version of their articles (or other works) to the ArXiv to make them publicly available before they are formally published in a journal. (The process of publication is often lengthy, and many consider it best to make the article available in advance, even though it probably has not yet been peer-reviewed.)
At present, there are around 1.4 million articles hosted on the ArXiv, and more are added every day. (Should you wish to see a visual representation of the articles on the ArXiv, which I assume you do, you should visit paperscape.) In the sub-topics that I watch, there are (approximately) between 4-10 new papers added per day, and these topics are not amongst the most active on the ArXiv. The problem then is to filter the daily uploads to find the papers that are likely to be of interest for me. Luckily, about the same time that I started to think of an automated solution to this problem, I discovered that the ArXiv has some tools that can help with this problem.