Maya 2012 came with a nice looking dynamics plugin called physX and it creates a shelf when it loads.
However I don't like the way this becomes the active shelf every time I start maya. I suppose I could unload the plugin, but then I'll have to reload it every time I need it. Fortunately physX uses mel scripts to initialize the plugin and create the shelf, so I modified one called physxUI.mel and added some code to re-select the shelf that was active before physX loaded.
If you are fussy about your active shelf and want to give the mod a try get physxUI.mel from my downloads page and drop it in your local scripts folder.
update: I tried this fix on another computer and it did not work. I'm not sure if I got lucky with the first one or unlucky with the 2nd. I think that success or failure has something to do with the order that maya does things at startup. Based on that theory. I've changed my modification slightly, so you'll need to download it again. And there is now an extra requirement: In addition to dropping the new physxUI.mel mod into your local scripts folder, you must also add the following line to your userSetup.mel
source physxUI.mel; storePreviousShelf();
This is now working on every computer I've tested it on. Yes. Both of them!