How to change the "Sign me in automatically" text

The text for the checkbox is located in the file C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\CONFIG\Resources\wss.en-US.resx under the key "login_pageRememberMe". You can either change the value in this file or edit the reference to this key in the login.aspx page where you can point to a custom resource file or hard-code the value in the .aspx page.

When editing any resource file, keep in mind that they are subject to being overwritten during repair or upgrade installations.

Quick update for anyone else that may need this info.  If the portal/website has already been created, the file will need to be modified here:

C:\inetpub\wwwroot\wss\VirtualDirectories\<port>\App_GlobalResources