Besides being enjoyable and a learning experience, side projects also provide an opportunity for a designer to showcase their skills. A designer may be hired by a client to do work very similar to his or her side project. With side projects it seems as though designers have a public outlet for personal work. It is also turning out to be a great way in which a designer can market his or herself for the kind of work they want to do, be it more illustration or hand done lettering.
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40 Days of Dating
Nicholas Felton's Annual Reports