Can I use dryer lint as a nesting material?

Birds will take the fluffy lint if it is put out. However, lint makes nests very unstable. Take a ball of lint and wet it. See how it shrinks? As it dries, it gets crusted and loses its fluff completely.

Male House Sparrow carrying material for the nest

There are better options for offering nesting materials to birds.

You can put out dog or cat hair that has not be treated for fleas or ticks.

String or yarn are great nesting materials. Make sure the pieces are only 4 to 6 inches long so the birds don't get tangled.

Many birds use small twigs for their nests. If you have any left from your winter cleanup, place the twigs in a nook in your backyard where birds can retrieve them. If you have an open compost pile, birds may visit looking for suitable nesting materials.

Dry grass from lawn-mowing is a good nesting material. But if your lawn has been treated with pesticides, don't leave the grass on the lawn or place in a pile where birds can get it. Any chemical that kills weeds or insects could harm birds, their eggs or their hatchlings. 

For your convenience, The Bird House has packages of nesting material. The packages contain a variety of sterilized material: feathers, string, cotton, hemp and Aspen fiber. All sorts of birds will find something they like for their nests.

In addition, we have bell-shaped cages that can be used to dispense nesting material. The cages can be hung from shepherds hooks or tree limbs. These cages make the nesting material very visible to birds. 

Finally, you might consider creating and maintaining a small mud puddle in your yard. Robins, phoebes, and Barn and Swift swallows use mud to form their nests.

From the Bird House: cage with nesting material