A Solution for using a laptop as a VGA monitor
I spent hours searching forums for a way I could use my laptop as a VGA monitor for other PCs and finally found and tested a solution! (by the way I've seen the VGA to USB adapters from epiphan but these are just way too expensive and my solution is less than half the price of those).
My Reason: I've got a headless PC that only has a VGA output and I don't have a monitor for it and didn't want to buy a VGA monitor since it runs linux and I don't need a monitor most of the time (only when something goes wrong and it drops off the network).
My Solution: I purchased a VGA to AV (VGA TO Video/SVIDEO) signal convertor and an EZCAP SNAPSHOT USB 2.0 Video capture device (found them on Amazon from a company called ClimaxDigital). My VGA output from the linux PC connects to the VGA input on the signal convertor and the svideo output from the signal convertor connects to the svideo input on the EZCAP SNAPSHOT. I then plugged the EZCAP into my laptop USB port (after installing the drivers for it) and used VirtualDub to show the VGA output from my linux box (also had to set the Device to "USB 2861" and set the video source to "Video SVideo" in VirtualDub). Voila! - I can now use my laptop as a VGA monitor for any PC that doesn't have one and I can easily carry these two devices in my laptop bag for use on customer sites etc to work on servers with no monitors.
This solution works perfectly for me, takes up very little space (both the VGA to AV signal convertor and EZCAP SNAPSHOT are fairly small and very portable - you could fit them in your pockets if you had to), plus it doesn't cost a fortune (about 60 but if you shop around and get more cheaply made products you could probably cut the cost a bit). In any case it was much cheaper for me than buying an LCD VGA monitor and it also gives me two useful tools I can use together or separately for other purposes (e.g. can use the VGA to AV to watch videos on my TV from the laptop VGA output - my laptop has no svideo outputs!) and the EZCAP SNAPSHOT can also be used to transfer videos from a camera or video player onto DVD.
I hope someone else finds this useful.