Two methods for spacing objects evenly are:
 
 - Select all the objects you wish to space evenly, then select Align
   to Autogrid from the Arrangement menu.
 
 - Make evenly spaced copies of an object by duplicating the object and
   moving it the distance you want.  While the duplicate is still selected,
   duplicate this duplicate.  Each subsequent duplicate moves the same
   distance as the first duplicate you moved.