Based on my experience, workers that take the time to thoroughly document their performance are a minority. With the changes in the economy and resulting impact on companies business performance, it's essential that workers take a renewed interest in the organization's strategy and how it impacts the customer base as well as your own business commitments.
There are a number of tools available for documenting your activities. Choose one that works for you. I personally favor Microsoft's OneNote 2007. More importantly, when you document an activity make sure you state what the impact was either on your ability to provide new services or perhaps how it saved the organization money or increased customer satisfaction.
As always, my mantra is that you have no control over what a company will do in the future regarding your job, however, you DO have control over your own actions and preparation for improving your marketability to others.
Bobby