Which MacBook models support (directly or indirectly) dual DVI monitors, for a total of three screens?
You only have two options, and they're both supported by all current MacBook Pro and MacBook Air models:


Use a DVI splitter to spread a single DVI output across multiple monitors (which will look like a single external monitor to the OS). The maximum resolution for an external monitor on all MacBook Pro or Air models is 2560 x 1600, so your maximum for the split displays will be 1280 x 1600 each (or maybe 2560 x 800).
Use a USB graphics adaptor for the third monitor, which will thus not have hardware graphic acceleration.