yes to the PC off the zaurus thing, however itwill stuff up your Z's ability to read the 3rd drive partion, or if you dont want to share files between your Z and the PC then you can do it with a file backed block device
basically its a matter of playing with the modprobe cmdline args, then pulgging it in and setting it up like a regular usb distro
instead why not use PC-net and VNC or X11, run samba to copy the files from theZ such as an xserver or vnc viewer and then run the apps on the Z, not the best solution if you are running the stock firmware but if you are using pdaXrom or OZ it can be quite nice. then you dont have to worry about keeping you settings in sync. i relise there may be a HP issue there
as for turning a normal distro into a usb one, the teqnique is not that hard and the "lots of writes to flash" is simple to evercome, in fstab make /tmp a tmpfs, depending on if you want logs or not you can do it for /var as well (not recomended). the real flash wearer is syslog, so if you have /var as tmpfs you dont need to worry otherwise you might want te tell it to not flush the buffers to disk so results get cached for awhile, that and enable laptop mode which will delay it even futher
if it crashehs you dont get the logs but i rarley use syslog logs to fix a computer that crashehs at random, i normaly use it for setup and config problems, so tmpfs is probely all right
noatime is somthing you might want to add as well, if you are really brave you could hack the OS to be mainly RO, but this requires in depth knowlage of the file system hiracy and how the prgrams you run interact with the system, before i orget, /dev can be tmpfs because it only gets written at boot and its contents are dynamically rebuilt
that said some distros work better than others, debian and gentoo are probelly 2 of the best to convert (knoppix is bassed of debian) but YMMV
app selection is important, did you know zsh syncs on every command, i didnt at first and couldnt work out why my HD kept spining up when testing laptop mode on the Z
the other option you have is to load the FS into a tmpfs then piviot root, ifyou have home as a seperate partion then you can mount it to keep your settings however this can make things like program updates hard to do
if you want more info just post what you need
