Lets say I have a 3D model of room in some format. How can I programmatically render "spherical" panorama from some point of room (kind of like the "Google street view" uses)?
I suppose it can be done in Blender?
It's better if it will be done in Linux.
I'd say your best bet is to render cube maps and convert these to the desired projection. IIRC HDRshop is able to convert cube maps to sphere maps. To render a cube map, just point a camera with 90° FOV along each positive and negative coordinate axis.
If you want a static image, render the images like Malte says, and stitch them back together with http://hugin.sourceforge.net/
If you were looking for something interactive, you can render it in the blender game engine, and look around inside, or even project it into a dome.