Logger is an addon that logs various in-game events such as exp gains, skill ups, and items looted. Other features include a search feature, selective event display, and a summarization function that will sum up certain events. (for example, how much faction you have gained in a selected time period) Logger is particularly useful in accurately gauging how much one farms (i.e. ore, herbs) over a period of time.
Type /logger at the command line to use.