I can vouch for Jaycar, Altronics and X-On as an online source within Australia. But there's also Oatley Electronics, RS Components, Wiltronics, Prime Electronics, WES Components and Harbuch X-on. Oh and Dick Smith and Tandy for what they are worth.
RS also has a sales counter at their warehouse in Sydney which could be very appealing (their cattle dog is the size of a Sydney telephone book). Jaycar, Dick Smith and Tandy have a number of retail outlets across the 'burbs. Oatley, Prime, WES and Harbuch are all based in Sydney too