Easy you need a USB board for your amiga and the POSIDEON USB stack for your Amiga
I have a SPIDER USB 2.0 card from Elbox
all I do is plug my Sony camcorder into the USB port and it apears on my desktop just like a floppy or a CDROM I can copy,format,make drawers rename,and transfer files just like you do everything else on the Amiga. I also purchased a PNY Seven in One USB 2.0 media reader I plug in a smart media,flash,memorystick, they apear on my desktop and I can tranfer files back and forth,
even between the different media faster than most hard drives.
play back my MPEG's using Frogger use multiview to display the JPG's. Posideon also includes drivers for a Aptec's Three in one Pen Camera if you have VHI you can use your USB camera as a Web Camera.
Posideon can be purchased from IOSPIRIT
http://www.iospirit.de/ for About $20.00 American. Cost on Amiga USB cards depends on your Amiga setup. but they all use the Posideon Software some cards come with a licensed version included others just supply the drivers and you have to purchase Posideon on your own.
I havn't tried to use a USB mouse or Keyboard since my mouse and keyboard adapters are outstanding. My scanners are SCSI and my printers use Par. ports so there I Haven't tried to use a USB version of them. But they are supported.
There is also a Posideon list on egroups
http://groups.yahoo.com/group/highway_usb/Kurt