http://www.drobo.com/ Drobo's hardware seems to match most of your requirements:

• Redundancy - You can lose one (or two) drives at one time without data loss
• Compatibility - Compatible with Win 2000/XP/2003/Vista, OS X 10.4 and later, and various flavors of linux
• Portability - You can pick the enclosure up and carry it to another computer
• Portability - If the controller dies, you can pop all your drives into a new Drobo and there will be no loss of data or need to rebuild the array
• Expandability - You can add new drives whenever you like, with no size, manufacturer, or model restrictions
• Ease of use - Initial setup and format of my Drobo took less than 20 minutes, the last 15 minutes of which were automated. When adding new drives, they will be automatically added to the array and available within 60 seconds, with no user interaction required

The one downside of a Drobo is vendor lock-in, if your controller dies. However, this seems to be the case with every RAID controller.

I'm buying my first Mac soon and i'll need lotsa software. Would you mind sharing your favorite Mac apps site(s).