I went through this very thing earlier this year. 
You may have to experiment a bit to see what work flow is best for you. I’m truly cross-platform and I use OS X, Linux and Windows. I wanted something that would be cheap and portable, yet I’m willing to pay for something if it works. Here are some of the things I tried:
PCB layout:
Eagle
gEDA
Kicad
Kicad and gEDA work great if you’re not on a Mac. :( Fighting to get them working was losing me time, money and sleep, (I want to layout boards, not recompile software - I do that enough at the day job!) so I went ahead with the full version of Eagle. I’m still learning it, but I think I made the right choice - it’s the most common program in DIY circles, there are lots of Eagle projects out there on the web to download, and it works on all three platforms I use. Plus, I’m a POVray user, so I like Eagle 3D - http://www.matwei.de/doku.php?id=en:eagle3d:eagle3d
2D Graphics/Panel design:
CorelDraw
Front Panel Designer
Illustrator
Inkscape
This is especially an area where there is no winner or loser (of course, if you’re using Linux, you get to choose Inkscape, and Mac users get to choose from Illustrator or Inkscape). I do my own silkscreening, and for whatever reason, pretty much the whole silkscreen world uses Corel, so it’s easier to go with the flow. Illustrator and Inkscape are fine as well - knowing Illustrator isn’t a bad thing, especially in the professional graphics world, and of course, Inkscape has the best price, although it seems as if the Inkscape native file format is on the wane.
Now, if you’re going to have a lot of panels made, it may be worth downloading Front Panel Designer from Schaeffer or Front Panel Express. (It only works on Windows - did you get your free copy of Codeweavers CrossOver yesterday?) The program itself is free and makes it easy to design panels and have them made - you just email the design file to the company and you get that panel delivered to you exactly as you designed it - great for prototypes or small quantities. For larger quantities from a cheaper vendor, or if you want to have them drill your panel and have someone else do the painting/marking/screening, you can buy a DXF file export add in from them for $150. I use that DXF export tool a lot myself - makes it so much easier to transfer info to Corel, TurboCAD, use in my own CNC tools, etc…
CAD/3D design:
AutoCAD/AutoSketch
Blender
POVray
Rhino
Sketchup
SolidWorks
TurboCAD
Wings3D
I looked into a lot of different CAD programs, but I decided I really wanted something that supports 3D. You can divide the 3D world into different parts - modeling and rendering, etc - lets look at modeling. OK, if you’re looking for free 3D, look no further than Blender. Great product, great support. Only problem is it doesn’t really play nice with anyone else. Sigh. Other modelers I looked at were Rhino, Sketchup and Wings. (Let’s go reverse alpha order on this…) Wings3D is a free subdivision modeler and works quite well, other than the fact that it doesn’t import or export DXF files. Sketchup is another free tool, this one from the evil empire over at Google - it’s great for quick mock-ups, especially when you use the “draw-a-geometric-figure-and-extrude-it” method. Again, output file formats are limited, but you can buy “Sketchup Pro” for $500 and get the ability to work with DXF files. (I’m getting ahead of myself here, but TurboCAD can read SketchUp files, so if you use TurboCAD you won’t need the Pro version of Sketchup.) Rhino…ah, Rhino, what a great program! I think this is one of the finest modeling programs available. It uses NURBS, which means you end up with superior curved surfaces. Other modelers use polygons, so if you want a tight curve, you have to use more and more polygons to simulate that. Rhino is usable for both 3D modeling and CAD work - you can design with as much accuracy as any other CAD program.
Speaking of CAD programs, well, there are a lot of those too. Solid Works is the current king of the heap, along with a couple other high end packages (Pro/E, AutoCAD, etc). Sadly, Solid Works *starts* at $4000 (US) and goes up rapidly. AutoCAD isn’t really much cheaper. While not as glamorous as Solid Works or Pro/E, TurboCAD is definitely the low price leader. I was about to buy TurboCAD Mac for ~$150, when they had a sale on TurboCAD Pro. (If you can wait for the sales, you can save quite a bit of money on TurboCAD! Download a demo and get on their mailing list…) With version 15.2, TurboCAD just added support for importing Rhino files too.
Before I forget, back to 3D rendering for a minute. I use POVray, since it uses a text file for scene description. (And it’s free, which doesn’t hurt!) Most of the pictures at http://www.midiboxaddict.com/mb808/case were created with POVray. If you’re a programmer, you should be able to learn POVray in an evening. I really like it for rendering panels, since the text input file is very specific about locations, and if you use variables as in other programming languages, you can easily modify row or column positions, knob sizes, etc, by changing one global and re-rendering.
OK, recap - I use Eagle for schematic and PCB work with POVray and Eagle3D for pretty pictures, Front Panel Designer for panels, Sketchup for cases, CorelDraw for graphics, and TurboCAD to tie it all together. Works for me…