This is a guide showing the work flow I've been using to get parts out of Autodesk Inventor 2011 and into the vector format needed to send to a laser cutter. I've been using this quite a bit this summer for my internship, since the company happens to have a laser cutter in their shop.
First thing first, you need to design all of your parts in Inventor, or whatever 3D CAD program you happen to be using. Designing for laser cutting is relatively easy; A single sketch, extrude for the material thickness, assemble. You do want to consider the implications of having sharp corners being cut out of acrylic, or whatever material you're using. Sharp corners will make it more vulnerable to cracking.
drawing exchange format back in the 80's, which allows us to be able to export these .idw drawings to something Inkscape can open, namely the .dxf format. Inventor is a little screwy, because it has several different types of saving, with subtle differences. You can't "save as" a .dxf file, but can only "save copy as" a .dxf file, so make sure you select the correct menu option.
Now you should have .dxf files for each part. Next is to open them with a vector image editor (the de facto free one being Inkscape), and convert your parts into the .svg and/or .pdf files your laser cutter or laser cutting service expect.
Now all that's left is changing the stroke color to the correct one for cutting. This is because laser cutters will have several different power settings, for say cutting, engraving, deep engraving, raster, etc, and will distinguish between which modes you want to use by the color of the lines. My cutter uses red (#FF0000) for cutting, but others will use black (#000000) or blue (#0000FF), so make sure to read the documentation and check your settings. Select all of your lines, and right click the correct color at the bottom of the Inkscape window and select "Set stroke" This should now have you with vector files you can send off to be cut out.
Now, in addition to the basic outline from your 3D CAD program, you can also quite easily add notes on the material using the text tools, or pretty much everything, in Inkscape. Just make sure you remember to set the stroke of the text to 0.001" so it doesn't end up just rasterized, and turn off the fill if you don't want to pay for several minutes worth of laser time to shade in your letters (not that I totally made that mistake and turned a 45 second cut into 6 minutes).
And as always, print everything out on paper or cardstock beforehand, to save you the expense of noticing something obvious in $5/sq ft material.
Finally, consider the implications of that the laser will burn off about 10 thou of material where it cuts. For most applications, this isn't a big deal, but if you're trying to get some tight-tolerance fits, you'll need to move the cut vectors out about ~5 thou to actually get what you drew.