Most designers use 1024x768 as a baseline for website development. That allows them to use css grid systems like 960 & blueprint to easily outline content. Is there simila
Simply, no.
Lots of information here. http://www.quirksmode.org/mobile/
There are just too many devices with too many different screens to assume a common resolution. While it may be true that 320 x 480 can be found on many devices, it is by no means "common". You have to use flexible design principles and then use media queries or js detection to add a class to adjust your display to the proper dimensions. This is part of what makes mobile so difficult to wrangle right now.
This website is super handy. An up-to-date database of various devices and their screen specs.