Please see here: http://talk.maemo.org/showthread.php?t=38314

Currently in the situation you describe you need to press ctrl-backspace and then q to switch to the first application, w to the second and so on.

Single press to switch is not as easy, since there are no free keys (or even key combinations) there is no 1 key, and ctrl-q (for example) is already used by many applications.