Similar functionality is given by the xwd and especially by the xv program.
xgrab is an interactive interface to xgrabsc and allows you to do most of the setup with a mouse, and then uses the xgrabsc program to actually do the processing.
A hint for Xstation-users: xgrab (like some other X11-software) uses fonts not available per default. You can add this fonts by the appropriate xset command or simpler by the script xsetfont75 available in the /usr/local/contrib/bin directory.