180 Technology Tips is a great site that I learned about from David Andrade and is described as offering 15 hours of free training in just 5 minutes a day. The way this is done is by creating pages that are color coded to a key. For example, if you want to learn more about Excel, you would choose the designated color (green) and then any corresponding number to open a page w/ tips & hints (w/ screen shots).
What makes 180 Tips so useful is the ability to subscribe to their site and receive 1 tip a day via email so as not to get over-loaded.
Give 180 Technology Tips a look by clicking here.