I picked up a full copy of Corel X3 off the internet for $169US. It is actually a student version, but you get all the licence and autorization codes for it. The regular retail is $399 US off the net, so I got a good deal. For what I do, fooling around and stuff it is plenty good enough, even if it is sort of black market software. I pretty much use it only for converting bitmaps to vector format and it does a good job.
I have also tried out Inkscape, but most of the time, I have found Corel does a nicer job on scanned images in TIF format. I use Corel to trace the bitmap, then export the Corel image as .eps and bring it into Vcarve. The only problem in doing this is that Corel will make you a double set of vectors (dont know why), so you need to use the "select duplicate vectors" command in Vcarve and delete the double set, and you are good to go.
For actual CAD packages, you only need something to draw a 2D image, and be able to save it off as dxf, or eps. Both of these functions can be done with Autocad, but for the occasional user it is far too expensive. Autodesk also makes a cad program call Autosketch, which sells for about $170 or less on the internet. It is only a 2D program though, and I dont know if it will export .eps, although it will export .dxf files.
Apart from that, there are several 2D cad programs on the market that are cheap, or free, it all depends on your needs.
Turbocad is also a good program, selling for about $149 or less, off the net as well. Turbocad will read and write .dxf files for you.