Wow. CiteUlike is the best thing since Brian’s OPP blog. Here’s what it does: There are feeds for journals from all major publishers, plus arXiv and such. You can set up a watchlist of journal and other feeds, or other user’s libraries, and then build your own library of online papers, with keywords, comments, and ratings from “top priority!” to “I don’t really want to read it.” You can add articles via a bookmarklet even when you’re browsing JSTOR, arXiv, or publishers’ sites. Of course, you can also add individual papers. Your library, your watchlist, tables of contents of recent journals, etc., are all available as RSS feeds. Plus, you can export citations in BibTeX and EndNote format.