A free program for Android, by JelleK.

Just Sketch It is an Android app that converts photos into pencil sketches, comics, manga, or posters.

To start creating an absolutely fantastic effect, select a photo from the gallery or capture it with the camera. Following that, you can apply one of 23 different effects to your image and edit it as you see fit. Select from effects that include Color Sketch, Simple Sketch, BlackBoard, Comics, Dot Comics, Cartoon, Halftone, Manga, Pixelize, and many many more.

If necessary, crop your image. Then, choose a resolution and save your photos. You can also share your finished photos without cropping them on Instagram and other social media platforms.