Everyone knows you can use OS X's Login Items to start up certain applications when you log in, but its less well-known that you can use them to launch just about anything—including load certain web sites.
This feature is pretty useful if there are certain sites you want to check every time you start up your computer in the morning, like check your email, check the local weather, or something else. This works with any browser. All you need to do is head to the web site in question and drag the URL from the address bar onto your desktop. Save the resulting .webloc file in a safe place where you won't delete it.
Then, go to System Preferences > Accounts and hit the Login Items tab. Hit the plus sign and navigate to your saved .webloc file like you would any other app, and add it to your login items. From now on, when you start up your computer, your default browser will load up that web site for you. It's simple, but helpful if there are certain things you want to open when you start up your computer, but not necessarily every time you open your browser.
How to Open Websites at Login [Macworld]