Since posting my CAD rendering gallery page, I've been e-mailed many times about performing advanced operations such as threading, sweeps, and other such things. Thus, I've taken the time to create a few guides on how to perform some of these advanced tasks (below). Other tutorials might be coming soon, frankly depending on what you guys what me to write about (as always...).
Threading - add modeled threads and helicies to the holes you already have.
Importing images - Display 2d picture files on models over which you can trace.
Advanced/compound lofting - Creating advanced 3d surfaces using the Loft command.
Angled workplanes - Creating 3d features using simple sketches and angled workplanes.
Cylindrical parts modeling tips - Organization notes about making revolution-based parts.
2D Import/Export - Working between file types.
O-ring design - Example diameters used to create moving seals. (not really CAD specific)
I've been doing this type of thing for an extremely long time, so you have to know I'm happy to share any techniques I may have. However, there are a large number of other modeling programs out there, and I haven't used them all. I have expert knowledge with Inventor, Solidworks, and AutoCAD but those are the only mainstream programs that I'm confident I can assist you using. If you're using one of those and have a question, let me know.
Inventor v. Solidworks:
Out of the many CAD-related questions I receive, many of them begin with why don't you use Solidworks?. Well, the answer is I do use Solidworks, but only when needed. I personally prefer Inventor when working on my own, so I typically choose it when given the choice. However, since both programs are used heavily throughout industries (paintball or otherwise), I'm perfectly content using Solidworks whenever that need arises. This way I have the ability to cater for more companies and developers, since some programs aren't compatible with others; I'm flexible in this regard and it's helped me many times. I not only hold certification in both, but I have spent LITERALLY THOUSANDS OF HOURS with both programs, and simply prefer Inventor out of preference. Additionally, I own stock shares in both Autodesk and Dassault Systéme, just for the sake of it.
Like many other things, I find both programs to have their own advantages and disadvantages. In general, the abilities of the programs are identical; an extrusion is an extrusion, a loft is a loft, it's all the same rudimentary stuff. I believe Inventor has a more simplistic interface whereas Solidworks' interface is more feature-packed, making it more complex while at the same time giving it better control over some features or operations.
As far as I can tell, both programs are heavily used in industries. Most paintball companies seem to use Solidworks [out of those two] but in other manufacturing areas I see a lot of Inventor as well. It's difficult to gauge for certain which program is used "more", especially since both companies claim to be the #1 according to their own studies (although it's notable that Autodesk is a much, MUCH larger company). Nevertheless, in my opinion the decision between the two programs is NOT a make-or-break choice that will determine your success. Both are leading professional design systems and both are extremely powerful. That's my opinion and I'm stickin to it.