Dell do not offer any driver for Mac or Linux or anything but Windows XP and Vista. The best bet is to simply plug it in and try it out.
In Mac OS X 10.5, go into System Preferences and add it as a printer. You may need to choose Generic as the printer type. (In Mac OS X 10.4, use the Printer Setup Utility to add it.)
Also from System Preferences (or Printer Setup Utility), add it as a Fax.
Open the Image Capture utility to perform scanning.
Mac OS X supports most of devices without any additional software. However, in some cases it may only be able to regard it as a generic type of device and some functionality may be simplified or not available. In such cases, it is up to the vendor (ie: Dell) to provide software to support the extra/advanced features. But unfortunately (and not surprisingly), Dell don't.
