The best type of software for productivity is personal information manager (PIM). They are softwares which help you oraganising your personal information, such as contacts, calendars, emails, notes etc. To give you choices, find out what are available on the Internet and fits you, Listible has a huge list (over 160) of PIMs. There are Windows & Mac based software; web based, and all of them are free:

The list is provided by Listible. It is a new service where you can include any of their list into your web site. All you need to do is cut and paste a line of javascript into your web page (and even into your blogging software like WordPress!).