The Great Ocean Road is magnificent and every traveler (or local!) who has the slightest ability or inclination to go, should. I'll append this statement by saying that good weather is vital, although I'm sure mediocre weather would suffice as well.
The Great Ocean Road runs from Warrnambool to Torquay and provides fantastic coastline views and beaches. It's most well-known attraction is the 12 Apostles, although I thought some of the other stops along the way were even nicer!
Make sure you bring your camera and swimming attire and give yourself ample time to fully explore each of the areas, which are clearly marked along the road. You won't need much as far as an itinerary goes because it's pretty well signposted.
My sister and I went on a three-day, two-night tour with Groovy Grape from Adelaide to Melbourne, a decision we wish we had made differently. They took us from Adelaide to Melbourne, through the Grampians National Park, and along the Great Ocean Road.
In retrospect, we should have just skipped the Grampians (nice, but I've seen better) and headed for the Road instead. The Grampians are a little bit too far removed to lump into the same trip so we spent a lot of time getting in and out of there and not enough time along the B100 highway (aka Great Ocean Road).
I'd recommend doing this trip on your own, and it's actually pretty easy! Just find a rental car and drive! Directions won't be too much of a hassle (just keep the water on your left or right, depending on your compass heading) and if you need accommodation along the way, try The 13th Apostle Backpackers.
This trip can be done in one day from Melbourne, but my personal recommendation would be to spend two full days exploring the place.
I promise it will be worth it and it's a trip that you surely won't forget.