After I connect to the Internet, I like to launch Safari, Mail and iChat immediately, so I found an easy way to do this with Automator. Launch Automator and drag the "Launch Application" action to the Workflow pane. Select "Safari" from the drop-down menu on the action. Repeat this for all the other programs you want to launch. Save the workflow as an application and drag it to the Dock. After you connect to the Internet, click on the new application in your Dock and your programs will launch, one right after the other.

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