Yamli allows you to type Arabic using roman characters. For example you can enter the roman letter "f" for "ف". You can also use the Arabic chat characters. For example "3" for "ع", "2" for "ء", "7" for "ح", etc ...
Type it the way you say it. Try it out !
Couldn't be simpler. Now I just have to learn a few thousand Arabic words and I'm away. (Via The Inquirer.)