It depends on your nationality Julia. But there's a list of 63 countries whose citizens can obtain a visa-on-arrival. on the list are Australia, NZ, USA, UK.... a full list is here:
The visa fee is $US25 (but they take Aus, NZ and Indon currency). almost 5 years ago
Visa on arrival for 30 days, if you qualify - Australians do - but have the exact money if at all possible: $25usd, for example.
If you live in Sydney, Indonesia Consulate is in Maroubra. You will need to buy a visa if you're staying longer than 30 days. almost 5 years ago