I just thought I'd give a big thumbs up to the new Matrox Triple Head2Go. Just installed it last night and connected 3 x 19" Dell monitors to my laptop. Intstallation was a snap - made the connections, installed the software, set the configuration I wanted and that was it. I've never had so much screen space in working with a laptop. I've used various laptops as my only computer for 10+ years, and this Matrox device let's me still use a laptop as my sole computer, rather than having to set up a separate desktop computer to see all the charts I want without toggling between windows.
I just bought a dualhead and get really low resolution. The triplehead is not for everybody. Although I did the test and they said it was 100% competiable, still very low resolution. Just double check before hitting the buy button.
I have very good resolution on my monitors. Each 19" gives an equivalent of 1280 x 1024 (technically it's 3840 x 1024, spread across the three external monitors). I'm no expert in these things, but resolution may be a factor of the video card/driver you've got in your laptop.