Autodesk added a very nifty (yet undocumented) system variable in AutoCAD 2005: "OSNAPHATCH"
This system variable controls whether AutoCAD has the ability to snap to hatch patterns.
To change the setting of this system variable type "OSNAPHATCH" at the command line. There are 2 available settings:
"0" - Ignore hatches when snapping
"1" - Hatch patterns can be snapped to
Thanks to Michael Rotolo for submitting this very useful tip.