Hi Lumpy
As a former Tasmanian I think you will have a great (if slightly chilly) time down south.
Here are a few things to check out
http://www.islandcycletours.com/train.html
A local company that specialises in cycling tours, but also a good point of contact as owners are very active in cycling scene. COntact Sam if you are heading Hobart way.
http://www.biketas.org.au/
Bicycle Tasmania Advocacy group. Good for contacts and an idea of what is on and where.
http://www.cycling.tas.org.au
Tasmanian Cycling Federation (racing organisation) based in Northern Tas.
Bike Shops
Hobart
http://www.bpbikeride.com.au/
New-ish shop. Mechanic Richard is one of the best in Tas. Very good at knowing where to ride and may be able to help out with hire.
Launceston (northern Tas)
Cycle Torque and Coffee
The best shop in Tassie (former sponsor of mine and a complely biased opinion).
No Website but in Brisbane Street in Launceston. See Nathan.
A cafe in the bike shop. Short term hire available, good info on local rides.
Geards Cycles
Wellington Street Launceston. No web. A good bunch of young guys, quite into racing.
North West Tasmania
Derrico Cycles
Lots of other info available....any particular questions?