As far as walking goes, the best thing about Fraser Island is how many different options there are. If you manage to track down a decent map of the island – there's a good walking leaflet available from the City Council offices in Hervey Bay – then you'll see that there are loads of walking trails criss-crossing the island, and assuming you're self-sufficient (i.e. carrying a tent, food and so on), you can go pretty much anywhere you please.
You also don't have to stick to official campsites, because you can camp on the beach (as long as camping isn't prohibited; maps show where you can and can't camp). It's this freedom that makes Fraser Island such a fun place to explore by foot; I made up my route as I went along, just making sure I returned to the ferry a day or two before my rations ran out. If you get your timing a little wrong and run out of food, then there are plenty of pissed-up travellers burning round the island in their rented 4WDs, and they'll no doubt help you out with a beer or two, but try to bring everything you'll need, because the 'shops' are far from comprehensive. That's half the point, after all.
Here's the walk I did. Note that for the last part of the longest day, the 27.5km to Eli Creek, I got a lift from a lovely bunch of fishermen; it's not difficult walking along the beach, though, as long as you take your shoes and socks off and walk along the water's edge.
|1||McKenzie's Jetty to Central Station||8|
|2||Central Station to Lake Benaroon||7|
|3||Lake Benaroon to Seventy-five Mile Beach (3km south of Eurong)||21.5|
|4||Seventy-five Mile Beach to Eli Creek||27.5|
|5||Rest day at Eli Creek||-|
|6||Eli Creek to Seventy-five Mile Beach (near turn-off for Lake Wabby)||25|
|7||Seventy-five Mile Beach to Lake McKenzie||14|
|8||Lake McKenzie to McKenzie's Jetty||7|
Although the whole island is special, I highly recommend camping at Eli Creek and taking a day off to explore the Pinnacles, the wreck of the Maheno and the waters of Eli Creek; they're the highlights of an astounding place.