I think it's difficult to find any 24hr delivery after Dabao.com.sg closed down. I found a rather comprehensive list of food delivery services though.
Ripped it off from sgclub forum:
http://www.sgclub.com/singapore/any_24_hour_80227.html
I like to order pizzas from Oishi. IMHO, their pizza is the best I've tasted among all those that do delivery. Hmm I should try ordering from Sakae some day too. Having sushi delivered to the doorstep is like quite shiok man.
Fastfood (Burger and Chicken)
Carls Jr - 6720-2720(Marina Square), 6820-2726(Suntec), 6720 1670(Plaza Singapura), 6820-2720(Vivo City).
minimum order $30.
free delivery within CBD.
lunch time orders to be placed before 1130am.
KFC - new since July 2007 ! 6222-6111 (previously 6235-3535) (11am to 11pm)
minimum order is $12 (before GST). $2 delivery charge for all orders.
McDonald's - 6777-3777 (24hrs)
Pizza
Canadian Pizza (2-for-1) 6241-0241 (930am to 10pm).
Oishi (Japanese Pizza) 6555-5656 (10am to 930pm).
Pizza Hut - 6235-3535 (11am to 11pm)
minimum order is $12 (before GST).
For Pizza Hut, $2 delivery fee on orders made within CBD or Restricted zone/Orchard/selected Jurong and Tuas areas.
Pizza Royale (choice of Japanese, Korean and seafood flavours) - 6353-4567 (free delivery with minimum order of $15)
Sakae Sushi - 6388-8383.
Sakae Sushi also delivers pizza. See terms under Sushi section.
Indian/Vegetarian
Komala's (Indian vegetarian food) - 6392-2224 (9am to 9pm).
Brinda's (halal Indian food) - 1800-2746327 (1800-BRINDAS) (930am-9pm).
Sushi
Sakae Sushi - 6388-8383.
Delivery hours: 12nn-10pm.
Hotline operating hours: 10am-9pm.
Minimum order $15 ($3 for delivery). Free delivery for VIP.
Third party food delivery companies:
Cuisine Express 6339-9883.
Cakes
Angie The Choice (dial-a-cake) - 6345-9898.
Emicakes - 6749-6782.