It is highly recommended that you use this feature for storing your password, if an application you use support it. For example, everytime you open Google Chrome browser that save online password for your convenience, if you choose to use auto-login when using Ubuntu desktop, it will ask you to enter your password to unlock stored password managed by Ubuntu's build-in password manager.
Although it's good for safety, some people feel that it is anoying to enter password everytime they use certain applications. If you think so, here I will show you how to disable this feature so it will be automatically unlock keyring then it will never ask for your password again.
First, open the Password and Keys application. Click the Ubuntu logo on near top-left of your screen to show the Dash, and search for "Password and Keys" or just "password" or "seahorse" (real name of the application). Open Password and Keys app that shown up on the Dash.
Next, on Password and Keys window, right-click on a password item that you will unlock. If you have more than one password item, just right-click on each of them. When the pop-up menu shown, click "Change Password".
Then you need to enter your current password (old password). Don't enter any password for your new one, or leave it blank.
You need to confirm that you will store unencrypted password. If you are sure that it is what you want, then just click "Use Unsafe Storage" button.
Now you won't be asked for a password when using an application that stores your password. It will be automatically unlocked because you set it to.
For Ubuntu 12.10 (Quantal Quetzal)
Update: 2012-11-12The updated package of Seahorse has been released for Quantal repository, so just need to upgrade your Ubuntu 12.10 installation. You can perform update/upgrade with this Terminal command:
sudo apt-get update sudo apt-get upgrade
The interface of Seahorse in Ubuntu 12.10 is a bit different from previous version. After installing the latest Seahorse, open it, then to show the login password, select "View" menu ==> check "By keyring" (see the screenshot above), then right-click "Login" password on the sidebar. Then the next steps is similar to the above: enter your current password but leave the new password blank, and click OK to confirm unencrypted keyring.