With the recent release of OKFN's DataPkg for CKAN 0.7a it is as important as ever to get the latest version when installing. The source code is available from a mercurial repository and this is the best place to download from. 

Public Library of Science Automated Download Methods

Via email from PLoS Webmaster

Dynamic FeedFlares using AppJet server side Javascript

In this example, if the item category is "Music" then return a custom link, else show nothing.

AppJet

http://appjet.com/app/3454754/source

/* appjet:version 0.1 */