Convincing organization to move towards Open Source GIS?

To start with I'd throw out the whole open-source vs proprietary premise and look at it in terms of "does Tool A accomplish what we need in a better way than the Tool B we are using now?"

Then follow up with demonstrations and tangible examples of where the tool you are suggesting as an alternative gives better results, or comes at cheaper acquisition price, maintenance price, learning curve, and so on. Be fair and balanced, don't gloss over areas where the alternative is weak or has gaps.

An often raised point against open source and for commercial is support, having someone on the end of the phone or email to answer questions. Take a good look at the support the organization is actually getting now from the paid tools. How many times and to what depth are the questions answered by that paid tech support versus just "from the internet"? Actually collect data and examples for this. As before, be fair and balanced.

If the answers to any of these explorations are extremely heavy on one side or the other, chances are there hasn't been enough homework done. There is a lot of value in proprietary products, and there is also a lot of value in open source. The question is do those value points align with your business?

Also remember that it's not an all or nothing proposition. The S in GIS is System, a web of interconnected parts and processes. Add in or replace components with open source, where that makes sense.

And finally, just use it yourself. When someone asks, "how did you do...?" Show them!

My process has been to install, and find projects/champions to utilize it "under" the radar.
Doing small projects that have a high success ratio, and getting others on the same page with you will have huge effects. Also using the software in a non-pressurized environment will help it accomplish success and help you learn to accomplish with it.

When you have more understanding of what it's strengths/weaknesses are you will be able to apply it as a tool in larger projects. This will also hold your integrity together allowing others to see that you are not trying to "throw out" the system but to augment the system.

When you can add accomplished users without paying the huge costs of established license management. Then work hard to add project specific payments to OS developers. This will make the ROI much easier to track and present.

Much more could be said on this subject. I am sure others will have excellent advice also. Let's keep it constructive though or it will likely be voted as "Not Constructive"

Managers are not likely to cut off their employees from time tested ESRI tools without grass roots support. Imagine the alternative--say your company only uses open source tools to accomplish GIS related work. If all of the sudden ESRI tools were imposed on you, there would be a significant reduction in productivity in the short term. Rather, managers are more likely to test the waters and see how a potential transition of tools will work--after all they are ultimately responsible for the bottom line.

I would take a grass roots approach and convince GIS staffers to switch over to FOSS rather than the higher ups. A one time bonus equal to a year's licensing fees divided up among the staffers would provide good incentive. Once the GIS staffers actually embrace FOSS, the managers will realize the potential cost savings and are likely to opt for the transition.