I would like my bit torrent client to continue sharing data even after my session times out and goes to the login screen. Running Lion.
It isn't possible, but why a logout? Set an active corner on your screen in settings, when you go too that corner with your mouse your display will be shut down but your apps will be running! To activate a hot corner you go to settings/desktop&screensavers/screensaver and in the left corner you see hot corners click that and choose a corner you would like. Click on put display to sleep and your done!
I found a better answer: Caffeine.
Caffeine prevents OSX from going to sleep. I can turn Caffeine on, then go to login screen. Guest account is available at that point, but my own session won't go to sleep until Caffeine is disabled or, if I set a timer on it, it times out.