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With this tutorial (unfortunately only in German) I managed to make some 3D-maps from Openstreetmap data and SRTM height data using Povray:
(To be honest, the left one is by me, the right one by maxbe)
For 3D (and 2D), try GMT, here is the gallery examples link:
For rasters, this is a nice plot in 3D (but it can be more detailed if needed): http://comments.gmane.org/gmane.comp.gis.gmt.user/18815
This tutorial may help you to get started: http://geophysics.eas.gatech.edu/classes/Intro_GMT/
GRASS is another neat option: http://grass.osgeo.org/screenshots/3D/
With the open source VTP - Virtual Terrain Project you can load custom elevation & imagery (VTBuilder) into an interactive 3D environment (Enviro), from which you can export a high resolution snapshot (pixel dimensions limited by your video card).
The default shadows can be a little harsh when draping topo map imagery, using a lighting factor of ~0.3 seems to work well.
It won't be an out of the box experience though, expect to spend some time learning how to use the software. It takes a bit to understand how the image sizing and tiling system works.
If you're after the ultimate in control and configuration, the best open source application I've used so far for fusing elevation and imagery into relief maps is the OSSIM project's ImageLinker. See the "How to create a shaded relief" tutorial.
Even more than VTP though, expect to devote significant time to learning.
Mostly your topo data is going to be in shapefile format to be visually parsed.
What you want to do is convert your the topo lines vector layer into a "DEM" or "Digital Elevation Model". I'm working on this too.
My plan is to use grass once I've gotten my topo data convert into some for of DEM like ".hgt". But I'm also trying out the main answer guy's tutorial because it looks like a faster route to the finish http://download.osgeo.org/ossim/tutorials/pdfs/HillShade.pdf
Here's a related question I'm finding very helpful How to generate a DEM from a contour Shapefile?
You should give osgEarth a try. It is layered on top of OpenSceneGraph.
In my opinion, it's one of the best out there for 3D map and terrain-on-demand from source data.