There is no native functionality in Salesforce.com to send an e-mail reminder when a task is due. However check out this useful discussion thread on LinkedIn to find out how others are trying to achieve the same.
Here is a list of all the useful URLs on Salesforce.com.
As URLs change frequently, if any of the following URL is not working, please leave a comment with details and I will update the URL. Also if you come across any other URL that is useful for Salesforce.com, do let me know. I will include that URL in the list here.More
You can view all the features that will be incorporated in Salesforce Spring 11 release. The videos are categorized under different sections, based on the products that Salesforce offers.More
Check out this great video presentation to understand more about cloud computing and why it makes a lot of sense for businesses.