Actually, many many modern video cards are capable of it (I've had fine luck with nVidias 5000FX series and newer - I've heard they all support it, also most newer ATi cards), though I will admit to keeping my Matrox G100 around for TV usage. There was a time in there from around 2000-2004 where support for modes lower than VGA was spotty, but it seems to have come back.
The issue is convincing the hardware to actually run in that mode. Windows especially won't like to do it without prodding (e.g. powerstrip), and X (Linux/BSD) will usually require a special modeline in your X config file. Also, until the OS loads everything will be running in VGA text mode or similar, which will cause damage if fed to to a standard res monitor. A common solution is to use something to detect the frequency of the hsync signal and either turn off sync of halve it if it is higher than 15k (a very small microcontroller is easily capable this, and I'm sure somebody sells a pre-integrated setup).
Oh, I should point out that sometimes it isn't the hsync that's the limitation, but rather the pixel clock. You can get around this (without sacrificing authenticity in the picture) by doubling the horizontal res and then scaling everything 2:1 horizontally. So you can run 1280x480 interlaced, but the pixel clock will be the same as VGA.