Everyone needs a way to organize both their work and personal life, but not everyone needs the same solution. For something fast and lightweight that covers all the basics, Vincent Danen recommends Osmo.
Most people require a little help in managing and organizing their life. Whether we like to admit it or not, most people tend to be disorganized and the reason why we have any semblance of organization is because we have and use tools to help us: pads of paper, PDAs, phones, groupware solutions, and so forth.
If you don't necessarily need a smartphone to keep things under control and a large groupware solution like Zimbra or Outlook is too much organization, there's a solution called Osmo, which may be the program for you.
Osmo is a little personal organizer for Linux. It provides a calendar, task manager, address book, and a note-taking application. It is light-weight and fast and does not require an Internet connection to operate. It is not meant for collaborative work, so if that is what you need, a groupware solution is probably a better fit. But if all you need is a personal organization tool or information manager, Osmo will do the job nicely.
Your distribution of choice may have Osmo pre-packaged and ready to use with it being a simple yum or apt-get away. Once installed and started, you see Osmo start in the Calendar view with the current day circled. Beneath the calendar is a space for taking notes -- a handy place to jot down quick notes as they come to you.
Each note pane is specific to the date of the calendar, so if today was the 14th and you clicked on the 15th, any notes entered in would no longer be visible, until going back to the 14th. A little black tick on the calendar indicates those days that have associated notes. If you need to use the note space as an agenda, the clock icon will pre-fill out the note space with a timeline of your specification: You define the start and end hours and the step (in minutes) so you can have a timeline of every hour from 8 a.m. to 5 p.m. if you like.
Moving to the Tasks pane allows you to keep a TODO or task list of items to complete. Here you can create new tasks that can have a due date, an associated category, and priority. Tasks can be made recurrent, so if you need a reminder to take out the garbage every other day, you can tell the task to repeat every few days. And task lists can be printed, so if you have a list of things to do but need the list with you, printing it out is a matter of clicking one button.
The Contacts section is simplistic, but provides more than enough information for a personal rolodex. You can include addresses, birthdate, nickname, various phone numbers, various online addresses (instant messaging, email, Web site, and so on), a picture, and a free-form text field to put in any notes about the person that you want to remember.