Much of the features of Parallels Tools can be worked around with a linux guest OS - ntp for setting the clock, nfs or samba for shared files, using X11 for desktop integration etc. Others are obviously non-trivial (custom video driver for X that resizes the desktop to fit the window - good luck!)
In the meantime, the one glaring omission is the inability to "shrink" a HD partition under Linux - rather than trying to produce and test a tool that could be installed under half-a-dozen different distros (which would probably mean distributing it as source), would it be easier to produce a LiveCD image/virtual appliance, with its own Linux or *BSD kernel, that did this job?
In the meantime, the one glaring omission is the inability to "shrink" a HD partition under Linux - rather than trying to produce and test a tool that could be installed under half-a-dozen different distros (which would probably mean distributing it as source), would it be easier to produce a LiveCD image/virtual appliance, with its own Linux or *BSD kernel, that did this job?