Wink! I am 80% convinced to join Singapore Marathon happening on Dec 4, 2011. Since it will be too costly to travel for a run, I plan to look for friends who are willing to accomodate me for (at most) 5 days in SG.
Details I got for this event are below:
When: December 4, 2011 (Sunday) – from 5.00am (Full Marathon – 42.195km)
Where: Esplanade Bridge (start point) to the Padang (end point)

According to them, updated map of the Marathon Singapore 2011 race route will only be available in October 2011.
These were all retrieved from:
http://www.singapore180.com/events/singapore-marathon#race-route-map
Full Marathon (42.195km)
For the first time ever, the Full Marathon will kick-off at 5am, 30 minutes earlier than previous years, at the heart of Orchard Road at the T-junction after Ngee Ann City. Runners will run pass landmarks such as Clarke Quay, Chinatown, the Esplanade, Singapore Flyer and the Marina Bay Sands Integrated Resort.
Half Marathon (21.1km)
Participants of the Half Marathon can also look forward to a colourful and spectacular run with runners set to be flagged off at the Sentosa Bridge.
10km Men / Women / Wheelchair Marathon
The 10km run will start at the Esplanade Bridge. Runners will then head towards the Central Business District before turning back towards the Fullerton Hotel, and then on to the Esplanade Bridge. From there on they will continue their way past key landmarks on the Marina Bay before stopping the clock at the Padang.