For applications to Canada it could take between 3- 4 months. For Australia and New Zealand, it could take between 1-3 months depending on your course (Coursework/ research).
For UK, it could take up to 3 weeks unless you want to apply for priority which takes 1 week.
For USA, it is a face to face interview and so it is based in your appointment date. You get the notice the same day.
Europe also depends on the country. For the face-to face interviews you get results the same day while for others you have some few months to get notification.
Visa application varies among the countries. The best thing is to always prepare your documents and apply as early as possible. During peak periods, visas might delay.