Hi TheCamino,
Welcome. Basically, there's not much you can do about altering the tax treatment on income you've already earned. What you can do there is try and maximise your deductions and consider options like contributing to super depending on your income sources - find a good accountant! I'm using Bentleys and the guy I deal with in QLD is clued in.
http://www.bentleys.com.au/index.cfm/Home
However, if you are doing quite well and plan to continue in the future, one of the most tax-effective vehicles you can arrange is a discretionary trust with a corporate trustee. This should cost you no more than $1500 and if you are a hands on type you could do it yourself for cheaper.
I have used this site to setup 3 companies. Basically it takes the info you input and produces the paperwork and advises you what you need to send to ASIC to have your company registered.
http://www.incorporator.com.au/
And I have used these guys 3 times to establish trusts. They can set up companies as well and seem quite reasonable price-wise. I have not used them for that purpose but they do offer that service.
http://www.acis.net.au/
I offer the above as do-it-yourself routes but you need to understand
what you are doing to follow that path. Only use these services if you are confident of what you need and are happy to arrange it yourself. A mistake in setting up the structure can cost you a lot down the track - a lot more than you save by doing it yourself rather than arranging these services through an accountant. So get good advice before making any decisions - an accountant can advise you on the best structure for your plans. It will cost now but save you bucketloads of tax down the track. I'd also suggest picking up a book by Nick Renton about trusts in Australia. I forget what the book is called but runs you through the different types of trusts you can establish and how they can be used.
If you do use a company or trust structure you will then need to open new trading accounts in the name of the structure in order to have the income treated accordingly.