You can use the btlaunchmany.py or the btlaunchmanycurses.py version of the client. Both of these are found in the official source distribution. The first parameter on the command line specifies a directory which holds a number of .torrents and their corresponding files/folders; the rest of the command line follws the same form as the normal clients (see What are the command line parameters for the BitTorrent client? )

(more here later)