I have just pushed out RaPT v0.2.1. New in this release is the ability to search the Rails plugin directory from the command line.
For example, rapt search authenticated would return you a list of plugins matching that search from the directory, with links back to the directory for more info and with URLs to the subversion repositories. The repository URLs can be used as the argument for rapt install [URL]. Now any plugin (that's listed in the directory â€” 395 of them at the moment) is easily accessible without having to discover or even open a web browser.
Install via gem install rapt or head to the RaPT site to download a copy.