If we had Solaris 10 with GNOME, you could just plug in a USB drive and a little icon would appear on the desktop, allowing you to transfer files. But since we're still in the Stone Age, you have to follow these steps:

• Plug in the USB drive. If it has a light on it, it should blink a bit and then turn off. Or whatever.
• Find out the number of the (virtual) SCSI controller it's connected to. You may have to do this by trial and error, by trying all the entries in /dev/dsk. The four numbers (c#t#d#s#) are Controller, Target, Device, and Slice. The T, D, and S numbers are usually 0 for USB drives, unless you have multiple partitions on it or something.
• Get the root password from somebody (obviously I can't post it on this public wiki).
• Become root (with "su" or whatever), and create some directory to serve as the mount point, for example "/mnt/flashdrive".
• Run "mount -F pcfs /dev/dsk/c#t0d0s0 /mnt/flashdrive", replacing the # with the controller number.

Now the files on your drive should appear in /mnt/flashdrive, and you should be able to transfer files. Make sure to unmount it (with "umount /mnt/flashdrive") before you physically remove it, or your files will get screwed up and you may have to reformat the drive.