I found, through Tomorrow, an interesting blog that's all about salaries in Singapore. Here it is - Salary.sg.
There are lots of interesting posts on that blog, including this nifty one which allows you to benchmark your own annual income (or anyone else's) against the general population of taxpayers in Singapore. Anyone tried typing in PM Lee Hsien Loong's annual income yet? Heheh.
The post featured on Tomorrow was this one - Median Income By Age Group. It tells you the median gross monthly salary of managers (the generalists) and professionals (the specialists), by different age groups. To get a more complete picture, you would want to plow through the original MOM report, but Salary.Sg's graph does give a quick, convenient snapshot.