For riding in dusk/dark lights are not only required by law but make riding safer. In general terms, lights fall into 2 categories. 'Be-Seen' or 'To-See'. Preferably a combination of the 2 should be used. Other considerations such as light coloured clothing and reflective vests/straps and tape is available also. You can NEVER be too visible at night!
Read Bicycle Victoria's review and recommendations on lights to consider read more >>>
VicRoads laws for lights
Note: Fines for the various offences are expressed as x amount of penalty units. The penalty "unit" represents a dollar amount that is specified each year. In 2007-2008 it was $110.12 Most fines are 0.5 penalty units ($55). The highest is 2 units ($220) - Failure to obey traffic lights. However the fine table doesn't match the penalty units specified in VicRoads - Road rules for cyclists
There are many light systems that utilise AA or AAA batteries (the rechargeable systems are usually a bit more initially but will pay for themselves in time on cost savings).
There are also the higher end lights powered by dynamos or hub generators. St Kilda Cycles offer possibly the most extensive range of these systems. Whilst more expensive, they require no batteries/recharging and have improved greatly in efficiency and lack the 'drag' that many remember from the older style setups.
Speak to your local bikeshop as to your needs, riding style and what they recommend.
Three LEDs attached to your helmet can be set on repeatative flash to really attract attention to your presence for other roadusers. The added height of being on top of your head, (not just down at bike height) ensures you can be seen in traffic and also enables you to highlight your presence to roadusers entering from sidestreets as you can turn your head and point the lights AT them!
Another (red) LED on the back of the helmet will make you more visible to others also.
These small LEDs are very inexpensive and run to $10-20 each and batteries are $3-4 each and can last for daily use for the whole winter.
Again, you can never be too visible, so these should be used in multiple in locations - clipped onto jersey pocket perhaps or clothes, bike etc.