I'm new to Sketchup so I'm not really sure If this is new to anyone else. I found a plugin that looks like it has been around since March 13th, 2008 ( Convert Sketchup SKP files to DXF or STL ). 
Like the link above reads, it's a plugin that will allow you to export a 3D DXF file, I had this up & running in less than an hour, that includes downloading Sketchup 7, installing the plugin, & exporting the 3D DXF (attached below).
I started out with a DXF file from my blog ( Design 203 ), it's a simple 2D file that I created with Inkscape 0.46. I open Design 203 (dxf) into Sketchup 7, export the 3D model with the plugin, now I have a 3D model.
This was really just a simple test, next I'll see If I can get some texture added, to the face of the 3D model, and maybe some rounded edges.
I couldn't believe how easy this was, to work with inside of Sketchup 7.
dxf file