Annoyed that tapping my trackpad was no longer being recognised as a mouse click after an upgrade to Debian Squeeze, I sought to have “synclient TapButton1=1” executed after login.

It would appear that both ~/.xinitrc and ~/.xsession are not used. Placing the above command in the file ~/.xprofile resolved the issue and I am now happily tapping my trackpad.
(tested when using GDM for logging in and Enlightenment for the Window Manager)