Which module can be used to get the number of logged in users per day and supports views?
Couple of options (haven't tested either one):


This sandbox project seems to track login time and provides Views integration: https://drupal.org/sandbox/AshishThakur/1614582
Login History also tracks login time, but does not have Views integration yet. A patch was started for this, but looks like it isn't complete: https://drupal.org/node/1402266