The direct route that Greyhound takes between Melbourne and Adelaide means that you miss out on the Great Ocean Road, but you can take a detour to
Halls Gap in the Grampians National Park if you're prepared to mess around with local bus connections.
The Grampians National Park is one of the best places to see kangaroos in the wild and there are some good hiking trails from Halls Gap, which is the main town in the park. The hostels here are excellent, especially
Tim's Place or the
YHA Eco-Hostel.
If you get off the Greyhound bus in Stawell you should be able to change for a V/line bus to Halls Gap, which is around 30 minutes away. The
V/line bus timetable shows a good connection leaving Stawell for Halls Gap but the connection is not so good in the opposite direction and you may get stranded in Stawell as the return bus arrives too late to meet the westbound Greyhound. You may want to check with
hostels in Halls Gap before you visit to check if they offer better connections (it is possible that one of the hostels may be able to drop off off at Stawell or Ararat to meet the Greyhound bus as hostel staff - and anyone else living in Halls Gap - frequently travel to these two towns). Another option is to hitch back to Stawell or ask around at the hostel to find other travellers driving to Ararat, Horsham or Stawell when they check out in the morning.