For "flow", on single track, Sparrow Hill. Sparrow doesn't have the views though ... just the track.
... and parts of the Bicentennial National Trail (the BNT) and sections of the Hume and Hovel Track (H&HT).
The section of the H&HT from Blowering Dam going south is popular with riders. There are rules about riding the single track on the H&HT, but I'll leave that one up to riders to determine. The rules are on the H&HT site.
The BNT site has info for bike riders, you will need the maps. It has taken me nearly two decades to get around the BNT from the Victorian border to Ebor in Northern NSW. The BNT gets very wild in places. On the BNT is the 'Six Foot Track' from Katoomba to Jenolen one of the friendlier sections of the track. I like the BNT because it runs through my suburb in the NW of the ACT.
On MTBR on 'What did we all ride on this Weekend', I've put some recent BNT stuff, sections of track from the Western Blue Mountains and the ACT, scroll back a page ...
http://forums.mtbr.com/showthread.php?t=290857&page=20
I've contributed to a thread on MTBR about 'Epic Rides in Aus'. Kosciusko is full on and there are back country tracks in the Bimberi worth exploring, that will knock your rock sox off ...
http://forums.mtbr.com/showthread.php?t=530640
Find an original copy of 'Wild Places' by Prineus and Gold and design your own rides, that's how I found the tracks by just exploring. There are very good maps in the original edition. In the reprint now sold by the Colong Foundation the maps are a bit small ... a book like this will get you out there, if you are fearless. It will take you decades to learn and find the tracks through the mountains.
I've not ridden the Great Divide Trail (the GDT) in Victoria, but those who have and have sent me notes, recommend it as a must to do.
The rail trail, from Lithgow to Newnes is special. The views and tunnels (with glow worms) are magnificent. An epic ride, just magic. Don't start this ride at the official track head, start the ride on the old disused track behind the old railway maintenance sheds in Lithgow. From Newnes, then ride into Rocky Creek along the fire trail through the Colo Wilderness, although this section from Newnes is not single track, it is rollercoster and is one of the most interesting rough rides that you can do in this country ... watch out for snakes, sunning themselves on the tracl. There are so many snakes it is like being in an Indiana Jones movie.
For true epic single track with fabulous views there is something called Loop #5 at Stromlo ... include the new sections of track, 'The Fang' and 'The Pouch' on the ride.
On the western slopes of Stromlo starting from Echidna Gap there is, Western Wedgetail (top section) then out to 'Magpie Rock', join the 'Pork Barrel' track, then across to the 'Deep Creek Track' down into 'Terminal Velocity' at speed go into the chute of 'Spin Doctor' cut across to 'Party Line' then back into the lower track of Western Wedgetail. This is the best downhill ride on single track that I know. Do this ride late in the day, and take your camera and take your time ... you will see hundreds of roos, many within a metre or two of the track and some excellent views of the Blue Range, the Mountains of the Murrumbidgee and the Northern Australian Alps.
Warren.