How to choose a CAS calculator?
Although in some studies (only Further Mathematics), normal non-CAS calculators are allowed too, I would recommend the sole use of CAS calculators for VCAA exams. Furthermore, I would highly recommend purchasing CAS calculators
first-hand sometime in year 10 and then use that CAS throughout your VCE studies. Try
not to change calculators during your VCE, as it is very important that you not only know how maximise your usage of your CAS, but also have confidence with your skills, and these only comes with experience. A distinction between CAS and non-CAS graphics calculators can be found
here.
Calculator use for VCAA MathematicsFurther Mathematics
Either one approved CAS or one approved graphics calculator may be used in Further Mathematics Examinations 1 and 2. A scientific calculator may also be used, if desired, in Further Mathematics Examinations 1 and 2.
Mathematical Methods (CAS) and Specialist Mathematics
One approved CAS may be used in Mathematical Methods (CAS) Examination 2 and Specialist Mathematics Examination 2 only. No CAS or calculators of any kind are permitted in Mathematical Methods (CAS) Examination 1 and Specialist Mathematics Examination 1. The use of a graphics calculator is NOT permitted in either Mathematical Methods (CAS) Examination 2 or Specialist Mathematics Examination 2. A scientific calculator may also be used, if desired, in Mathematical Methods (CAS) Examination 2 and Specialist Mathematics Examination 2.
Approved calculators by VCAA (as of 2012)
CAS calculators
In 2012, the following CAS calculators are approved by the VCAA for use in Further Mathematics Examination 1 and Further Mathematics Examination 2, Mathematical Methods (CAS) Examination 2 and Specialist Mathematics Examination 2. The full functions of approved CAS calculators may be used (that is, the memories of these calculators do not require clearing prior to entry to the examination).
Casio
Algebra FX2.0, Algebra FX2.0 PLUS, ClassPad 300, ClassPad 300 PLUS, ClassPad 330
Hewlett Packard
HP 40G, HP 40GS, HP 48G, HP 48G II, HP 49G, HP 49G PLUS, HP 50G
Texas Instruments
TI-89, TI-89 (Titanium), TI-92/TI-92 PLUS/Voyage 200, TI-nspire CAS, TI-nspire CAS with Touchpad, TI-nspire CX CAS
CAS Software
For approved schools only, students enrolled in Mathematical Methods (CAS) either by itself or in addition to Further Mathematics or Specialist Mathematics, will be permitted to use computer-based CAS software Derive, Maple, Mathcad, Mathematica, TI-Interactive, TI-nspire CAS and ClassPad Manager and stored files on a CD-ROM for examinations in these studies, where the use of technology is permitted, provided they meet VCAA specifications for the conduct of computer assisted examinations. Schools wishing to use computer-based CAS software should apply in writing to the VCAA for approval.
What to look for in a CAS calculatorFor any VCAA mathematical study, you want to have a CAS calculator that will make problems as easy as possible to solve.
The checklist of basic abilities you want for Further Mathematics: • The ability to sketch Cartesian functions
• The ability to gather data from a graph
• The ability to manipulate algebraic and trigonometric equations
• The ability to solve and algebraic and trigonometric equations
• The ability to tabulate data and produce graphs and statistics from that data
• The ability to deal with matrices
• The ability to produce both exact and approximate results
• The ability to store and recall variables
The checklist of basic abilities you want for Mathematical Methods (CAS): • The ability to sketch Cartesian functions and relations
• The ability to gather data from a graph
• The ability to manipulate algebraic and trigonometric equations
• The ability to solve and algebraic and trigonometric equations
• The ability to solve and sketch probability functions
• The ability to tabulate data and produce graphs and statistics from that data
• The ability to deal with matrices
• The ability to produce both exact and approximate results
• The ability to store and recall variables
The checklist of basic abilities you want for Specialist Mathematics:• The ability to sketch Cartesian, polar and parametric functions and relations
• The ability to gather data from a graph
• The ability to manipulate real and complex algebraic and trigonometric equations
• The ability to solve real and complex algebraic and trigonometric equations
• The ability to solve and sketch differential equations
• The ability to deal with matrices, especially in relation to dealing with vectors
• The ability to produce both exact and approximate results
• The ability to store and recall variables
Additional features that are recommended:• The ability to highlight, cut, copy, paste, undo, etc.
• The ability to create, save and open documents (including notes)
• The ability to have tabs in documents
• The ability to program
• The presence of templates for differentiation, integration, matrices, fractions, etc.
• The ability to connect to your computer to transfer files/OS
Other considerations:• What does your school use? (it is recommended to use the same CAS calculator as your peers, this is more important than you might think)
• Does the calculator have known issues of crashing, freezing, etc.? (especially during exams)
• Does the calculator have a good lay-out? (are the buttons laid-out for easy and fast use)
• Are resources available to help you use the calculator? (guides, textbooks, etc.)
• Are updates regularly produced?
• Is there calculator software available for your computer too? (emulators, link programs, etc.)
• Am I already familiar with my calculator (if this is you and you are in year 12, do NOT change calcs now)?
What NOT to look for in a CAS calculatorThe primary use of your CAS will be for use in SACs, tests and exams. Buy a CAS based on its functions to help with your success in these SACs, tests and exams, not for the following:
• Whether or not it can play games
• Whether or not it can store images
• Whether or not it is in colour
• Slight cost differences between models
• Whether or not it is new
• Whether or not it is aesthetically pleasing (colour, shape, weight, etc.)
• Whether or not it is touch-screen/touch-pad/click-pad/etc.
• How many batteries it needs, and of what type they are
Recommended CAS’s by VN (based on the above information and not in any particular order)
• Casio ClassPad 330*
• TI-89
• TI-89 (Titanium)
• TI-nspire CAS
• TI-nspire CAS with Touchpad
• TI-nspire CX CAS
*Known to crash during VCAA exams
What CAS calculator do I recommend?I recommend the TI-nspire CAS (Click-pad grey version). The benefits this CAS has over the others are enormous:
• It has never failed in a VCAA exam
• It has lots of buttons on the key-pad and the useful "special" ones are very accessible (pi, theta, x, trigs, etc.)
• It runs on the latest Texas Instruments OS and hence, isn't at disadvantage to the newer TI calcs
• The Click-pad works far better that the newer Touch-pad
• It is still cheaper than the newer version

Another calc that I'd strongly recommend is the TI-nspire CX CAS:
• It has never failed in a VCAA exam
• It has lots of buttons on the key-pad and the useful "special" ones are very accessible (pi, theta, x, trigs, etc.)
• It's a lot more portable than the older editions
Helpful links•
Guide to using TI-Nspire for METHODS by b^3•
Guide to Using the TI-Nspire for SPECIALIST by b^3•
Texas Instruments: TI-nspire Family•
Casio: ClassPad Family•
ticalc.orgGood luck! 
UPDATE: NEW TI-NSPIRE OS UPGRADE AVAILABLE 