Is there an easy way to detect tables that are no longer used by my Drupal installation? I find it annoying that tables from previously used modules remain. I'll simply drop them using phpMyAdmin if not, but its a bit of a pain, and involves backing it up for obvious reasons! ;)
I think Schema will tell you that. If a module leaves tables after uninstall, that's a bug, and you should open an issue.
After disabling and before removing the module run drush pm-uninstall 'modulename' in the terminal.(More info on drush)
Or through the website go to /admin/modules/uninstall.
The name of the module will still be found in the 'system' table, this can be deleted manually.