What is 3DPrintingPriceCheck? It does exactly that. Jonas Neubert, creator of the online service, just released a significant update to the service, which now includes STL upload, instant quotes from some 3D print services, more materials and even lead time estimates.
The service makes shopping for the best deal easy. You simply drag and drop your STL model onto the web page and it looks up (or estimates) the pricing and lead time for printing said model at popular 3D print services. The services covered now include: i.materialise, Kraftwurx, Panashape, Ponoko, Sculpteo and Shapeways.
But it's much more than simply pricing. Each report includes direct links to the service's description of the material and their particular design rules. You can inspect them to ensure that your print will actually succeed on the least expensive service. It's always better when things work!
3DPrintingPriceCheck also includes filters for service and material type. Using these you can quickly identify which services have the best prices for particular materials, or which service turns around your print fastest.