MeeTimer monitors your time online, grouping it into activities for more meaningful statistics.
It gives you easy-to-digest information on where your time is really going (include the % of the working week you need not have spent at work), so that you can take real steps to reduce wastage.
It also discourages you from procrastination, using LinkWarn and TabWarn to make you think twice before loading a new page.
As it runs all the time, every effort has been made to make it fast & light; and it benefits greatly from Firefox's inbuilt database for speed.
More information can be found at the website:
Please note, there are reports that the Options screen is not working properly on some Linux installations.