Many support applications come as Preference Panes, accessible through the System Preferences. You can:
- find them in ~/Library/PreferencePanes or /Library/PreferencePanes and delete them from there, or
- right-click and remove them in the System Preferences dialog itself
Also look under /System/Library/Extensions for Kernel Extensions that were added. Note though that manually deleting stuff here can cause serious problems.
However, that doesn't work for all of these, and each application you mention does it differently. You're right that manually removing files is not a good way to uninstall these programs. Therefore, the developers offer uninstallers:
SteerMouse has an uninstaller you can access by opening the SteerMouse app. Open /Applications/Utilities/SteerMouse and select Help » Uninstall….
Logitech Control Center can be uninstalled through the installer or a separate uninstaller application called "LCC Uninstaller". It should also be in the /Applications/Utilities folder.