The race is about to start, ladies and gentlemen:
Get a life. These forums are meant for answering questions, not for trying to start FUD wars.
So. Back to the issue: on
Linux USB devices website you can get a first estimation. Just search for Nikon Coolpix, and you will see that almost all Coolpix support Mass Storage Device standard. This means that on the Amiga USB stack (Poseidon) you can connect your camera and use it like a mobile harddik (you will need fat95 file system, though).
Take care as modern cameras support also PTP standard sometimes, so one may switch the camera manually to MSD standard.
If this fails (in case of Coolpix it is unlikely), get out for a 10EUR flash card reader, which will be supported in almost all cases.
Regarding USB host controller: if you have a plain Zorro system, you can use an ALGOR (PRO), if second hand available a HIGHWAY, or a Thylacine (only easily available in Australia, AFAIK). The first two cards come with a full OEM license for Poseidon (no additional costs), the last one will either be operated with the upcoming OS4 USB stack or with Poseidon (additional fee for registration).
The UltraBUS Zorro card has been announced over one year ago, but is not available up to now; moreover it is not clear which USB stack will be delivered with this card.
For PCI based systems there's the Spider (II) card, where you will need a Mediator PCI system with DMA buffer memory (aka: graphic card, like Voodoo3), the hardware dongle (aka: Spider) for the driver from Elbox and a registered Poseidon stack (additional fee for registration).
If you need some literature, check the (German) AmigaPlus magazine issue #136 (05/2003) for a comparison test of different USB solutions.
Michael