In the spirit of online applications here is one that I find extremely useful when needed and it is nice to know that such service exists. VectorMagic
is a simple service that provides a way of getting your bitmap or raster images to vector file format used in publishing. To say it is simple service is an understatement as after uploading your image you are presented with full blown application, which is also available for desktop, build with Adobe Air/Flex platform.
When needed, there is no substitute for free solution.