I have written the two CiteULike plugins for PLoS (Public Library of Science) and the Journal of Statistical Software. What it means is that you can add a paper from these journals to your bibliography in one single click when viewing its abstract in a web browser. All information (authors, title, journal, year etc.) will be automatically parsed and will populate a new entry in your bibliography.
You don’t need the code since it’s now part and parcel of CiteULike but if you’re interested, all the plugins can be found in the subversion repository. They are written in Python.