On Windows there is Dell's extpart which allows one to extend a basic system disk (NTFS) of a running system without downtime. It looks like this:
C:\>extpart.exe
ExtPart - Utility to extend basic disks (Build 1.0.4)
(c) Dell Computer Corporation 2003
Volume to extend (drive letter or mount point): c:
Current volume size : 66285 MB (69504860160 bytes)
Current partition size : 76285 MB (79990815744 bytes)
Size to expand the volume (MB): 76285
Boom done! No downtime, system disk is extended from within the OS that's running on the system disk. The above was copied from: Extending a Windows C:\ Dell EXTPart.
Is there an equivalent for a non-LVM ext3 Linux disk? This is for a lab environment, so the distro to use hasn't been selected yet, it will probably be based on a stripped down version of lubuntu which doesn't have Gnome but has the Lightweight X11 Desktop Environment (LXDE) instead.