I've gotten several sets of additional pages at the Embassy in Singapore. If you get in there first thing in the AM you can either wait 30 minutes or come back in the afternoon and grab it. Here is the link, the embassy there is incredibly helpful because most US citizens there are in a state of constant travel. They made me an emergency passport in 18 hours and issued a new passport in 10 days.

http://singapore.usembassy.gov/amcit...formation.html

As for the lack of space in your passport, I can't speak to Singapore specifically because I have a singapore employment card and thus don't need get stamped, but I suspect they will find a small corner to stamp. I used to worry about things like this and then in May my passport tore in 2 pieces in the middle of a SE Asia trip and I had to politely "ask my way" into Thailand, Vietnam and then Singapore with this 2 piece work crudely taped back together. Surprisingly, I was not turned away (although I was told in each case to proceed to the US Embassy the next day, which I didnt do in VN or Thailand because of lack of time). Then the US embassy in Singapore gave me a four page temp, which I promptly filled up with stamps the next week. Even with the full temp passport (and no visa in it) I was able to get Vietnam issue me a replacement visa in the SGN airport (which covered up some of my existing stamps becuase there was no open space) and then get Thailand and Sri Lanka to stamp on several corners. I admit I was prepared to walk back to the gate and buy a one way fare home.