Foreigners planning to come to Indonesia must hold a passport valid at least six months after the date of arrival. Foreigners who visit less than 30 days from some countries like Brunei, Chile, Hong Kong, Macau, Malaysia, Morocco, Peru, the Philippines, Singapore, Thailand, and Vietnam are allowed to enter Indonesia without a visa. On arrival, citizens from the those countries will be issued a 30-day entry permit which may be extended for a further 30 days.
Foreigners from following countries will be issued a 30-day visa on arrival for USD$25.00. The countries are: Algeria, Angola, Argentina, Australia, Austria, Azerbaijan, Bahrain, Belarusia, Belgium, Brazil, Bulgaria, Cambodia, Canada, the Czech Republic, Croatia, Cyprus, Denmark, Dominica, Egypt, Estonia, Fiji, Finland, France, Germany, Greece, Hungary, Iceland, India, Iran, Ireland, Italy, Japan, Kuwait, Laos, Latvia, Libya, Liechtenstein, Lithuania, Luxembourg, the Maldives, Malta, Mexico, Monaco, the Netherlands, New Zealand, Norway, Oman, Panama, the People’s Republic of Tiongkok, Papua New Guinea, Poland, Portugal, Qatar, Romania, Russia, San Marino, Seycelles, Saudi Arabia, Slovakia, Slovenia, South Africa, South Korea, Spain, Suriname, Sweden, Switzerland, Taiwan, Timor Leste, Tunisia, the United Arab Emirates, the United Kingdom, the United States of America, Vatican, and Venezuela.
Besides that, the visitors from the countries which is not included in either of the lists should apply for a visa from their nearest Indonesian embassy or consulate prior to leave in Indonesia.
For more information, you can check http://www.imigrasi.go.id/index.php