Some people like the order of the programs in the taskbar to be, shall we say, predictable. I am one of them.

Usually I achive this by opening the programs after a reboot in a certain order, but every once in a while I need a different program (urgently) first - or Explorer crashes - and then I am out of luck.
My hand still guides the mouse to the spot where I usually have the item, but then I need to spend extra time finding out where it is now.
I came across programs a while ago that would re-shuffle the items, but I didn't want to spend the memory to have that feature. But I gave up now.
I just installed one, and I should have done so a long time ago.

I decided to go for Taskbar Shuffle. It has more features than Taskix or Taskbar Button Manager and it still only consumes between 1MB and 4MB of RAM - and it is also offered free of charge - as are the other two (the author does accept donations).
Considering that I am up to the Gigabytes in RAM, I think I can afford the memory footprint now. Yes, I do hit the physical RAM barrier frequently, but I can always exit the app if I feel I need the extra little MB. By the way, you can also turn it off and keep it running if you accidentally keep re-ordering items - or you can set the program to only work while pressing a special key (selectable)

Taskbar Shuffle can also re-order your system tray icons and has a few other settings, one of them to change the grouping behaviour of your taskbar items.

One mention though - it does set itself to run at Windows startup (option can be turned off in the program), but it doesn't start itself after the install - so you need to start it manually at least the first time.