Dave has created a new sub forum Developing Drivers and Software for ESXi where you can find trickstarter's posts now. He recently added a third part about Compiling Drivers that deals with the odds and bits of getting the original Linux source code to a state that cleanly compiles for ESXi. This is great work and a must-read for anyone who is interested in building drivers for ESXi!
What is not (yet) covered there is packaging your driver (after you successfully built and tested it) in a way such you can easily distribute it. If you want to share your work with others I recommend building a VIB package and/or Offline Bundle. These are the official VMware software package formats, and you can produce them using my ESXi5 Community Packaging Tools or the VMware fling VIB Author.
This is what VMware created the IOVP (I/O Vendor Program) for - a special program for vendors that gives you access to the required source code, tools and certification processes needed to make your product/driver VMware Ready. It looks like this is only open to members of the Technology Alliance Partners (TAP) program, and it requires an application process and an annual fee to be paid. I think it's affordable though even for small shops.