There is no real legal obligation on an employee to provide notice when resigning. However, the employee should still use good judgement. If the employee wants to use the former employer as a prospective reference then the employee should be careful as to not burn any bridges.
The employee should also use caution if they are going to work for a competitor or third party supplier of their former employer.
An employer should officially acknowledge the resignation and ensure that all company policies are respected and that company property is returned.
For more information contact me a lawyer in Mississauga.
Also see my post on non-competition clauses and employment contracts.