Is gravitational lensing affected by dark energy? Is gravitational lensing affected by dark energy? I mean, despite the effect if cause on the expanding Universe, could dark energy cause gravitational or anti-gravitational lensing? 
 A: Yes, it is.
As rob writes, dark energy (DE) doesn't clump as dark matter (DM) does, and hence doesn't itself "bend" light. However, in weak lensing — where one studies statistically small deviations of a large number of sources — one uses both the relationship between the redshift and the distance of a source and the power spectrum of matter, both of which depends on the amount of DE. Hence weak lensing can be used to probe DE (see e.g. Huterer 2001).
A: One of the most compelling arguments for dark matter is that the gravitational fields of large clumps of dark matter cause gravitational lensing of light sources beyond them.  There are some nice papers that analyze multiple lensed images of distant galaxies to map out the locations of dark matter in nearer galaxy clusters.
Unlike dark matter, we don't have any evidence that dark energy clumps on galaxy-sized length scales --- or of any length scales.  Without nonuniformities, you don't get lensing. Compare looking through an eyeglass lens to looking through a plate-glass window.
