If you have a card reader, this is very simple. The card appears as an external hard drive. Mount the drive, then use your favorite file manager to copy the files. I use KDE and Mandriva 2008.1 (Spring edition). All I do is hot plug the card reader, Mandriva pops up a 'What do you you want to do with new media', I select open in Konqueror, navigate with Konq, drag and drop the pics. That is it.
You may be able to use a USB connection with those cameras directly. My Nikon works O.K. My camera supports PTP and mass storage. It has been a while, I think I use PTP to transfer files directly from the camera. Read your manuals for more info on what they support.
There are programs like Digikam that will work with many cameras. It all depends on what your cameras support. If you have card readers, go that way first.