I have had some success with usb docks like this Universal Docking Station by Kensington to connect one external display to my laptop while using the onboard vga port for another display. But that's only two displays and I'm shooting for three. All I do is develop software and work in Photoshop... no games. For the sake of discussion, we can assume a Thinkpad or equivalent laptop with Windows 7 (I'm hoping for a platform-agnostic solution). How could I do this?
UPDATE: Question #128311 talks about almost the same thing, but the only solution was a Matrox TripleHeadToGo. I don't like that solution because the matrol box merely makes windows think that it has one desktop that is x*3 pixels wide (where x is single desktop width). One problem with this is that the taskbar stretches across all monitors and always starts on the left-most display. Also, try telling a video to go full-screen... As far as the OS knows, full-screen is x*3 pixels wide (e.g. your video spans three monitors).
UPDATE: I should be able to use my existing displays, asuming my displays can run on VGA and/or DVI.