The suggested knoppix dd solution should work well. You might want to pass something like "bs=4096k" as additional argument to speed it up considerably (bs is blocksize. Default is 512k)
However you might want to take a look at mondo rescue again. It does not make a physical 1:1 copy of the harddisk, but it will recreate all partitions, resized to occupy the entire space on the new drive and install an mbr with your bootloader (lilo or grub that is). It's easy to use too.
regards, Andreas Micklei