For those of you who are planning to use Singapore's public transport intensively or to stay in Singapore for a while, getting an EZ-Link card might be the right thing to do. This electronic stored-value card is accepted on most of Singapore's public transport means, including buses, MRT and LRT (Light Rapid Transit). EZ-Link cards are also being used for payments in McDonald's, 7 - Eleven, food centres, supermarkets and libraries, and even to buy soft drinks from vending machines.
The EZ-Link will make your life easier, when traveling around Singapore, as most public transport requires exact change when you pay cash and doesn't give change... When you pay a fare with EZ-Link, you simply place the card on the reader, located next to the fare box, and the fare gets deducted automatically (you won't even need to take the card out of your wallet).
A new EZ-Link card costs a minimum of SG$ 15 : non-refundable SG$ 5 for the card + refundable deposit of SG$ 3 + minimum stored-value of SG$ 7 (although you can load much more value on your card, if you wish...)
EZ-Link card can be purchased at any MRT station (at the Passenger Service Counter), as well as at all TransitLink ticket offices (located at the large bus stations/interchanges). The card can be reloaded at any MRT/LRT or bus station, either by using the Add Value Machines (AVM) or the General Ticketing Machines (GTM), located at the various MRT stations. You can add between SG$ 10 to SG$ 100 each time.
When you don't need the card anymore (like when you want to leave Singapore), just return it and you will get your SG$ 3 deposit + any leftover money.
A small tip from 'Metropolasia-Man':
A newer and much better product of EZ-Link is the Singapore Tourist Pass (STP) which allows unlimited use of almost all public transport (except some niche bus services, like the Chinatown Direct or the Night Rider)
At the time of writing, the Singapore Tourist Pass is sold at an introductory price of only SG$ 8 per day, and comes in three options: 1-Day, 2-Day or 3-Day pass (SG$ 8 / SG$ 16 / SG$ 24 per pass, respectively). There is also a SG$ 10 refundable deposit
The pass can be purchased at the ticket-office within the large/main MRT stations (Changi Airport, Orchard, Chinatown, City Hall, Raffles Place, Bugis, Harbour Front and Ang mo Kio), as well as at the Singapore Visitors' Centre (either the one on the corner of Orchard and Cairnhill, in the city, or the one in Changi Airport) and at True Heritage Brew in Clarke Quay
For more information, you can visit the Singapore Tourist Pass website (they sometimes have all sorts of promos, worth knowing about)
You may also want to read about...
To and from Changi International Airport
Transport to tourist attractions and Hop-on, Hop-off buses
MRT - Subway
LRT (Light suburban train), Trishaw and other means of transport