December 23, 2007
A feature that has been requested for a long time, Angled Guidelines have been implemented by Johan. They will be usable in the next release (0.46) of Inkscape.
All guidelines are "angled", horizontal and vertical guidelines being angled at 0 or 90 degrees. To change to a different angle, just double-click the guideline you want to change and enter the values. You can also create a guideline with another angle by dragging the guideline from the ends of the rulers.
Wiki
Now, Inkscape also provides angled guidelines! Double click on a guide to set its angle.
Can this be done in the development version now? When I double click on a guide to set the angle nothing seems to happen.