Install from ISO
download ISO image
record it to CD or use for install to VMware/Xen VM
Prepare USB stick for install
download USB image - with '.usb'
record it to USB stick:
from Windows - try to download and use tool: http://devzone.sites.pid0.org/OpenSolaris/opensolaris-liveusb-creator
from installed DilOS: apt-get install usbimgtools
usbcopy2 <USB image>
or
iso2usb <ISO image>
From another Linux/Unix - try to use 'dd' tool with USB image