As a writer Callen has written 20 full-length plays, a full-length adaptation, a one-act play, and about 50 monologues that have been produced. The monologues he wrote for a cemetery tour, Talking Spirits, received two awards. The first was a 1999 Award of Merit that the program received from the Wisconsin Historical Society. In 2003 the first four years of the project received an award from the American Association of State and Local History.
In addition he has had poems, articles and essays published in various places, including The James White Review, The Sweetwater Review, Out!, Scott Stamp Monthly, Our Lives magazine, and the Wisconsin Fellowship of Poets' annual poetry calendar, among others. He self-published a genealogical work on his great-great grandfather and great-great-uncle, The Townsend Brothers of Shullsburg, Wisconsin.
As a photographer Callen has won awards and also has had two one-man shows in Madison, Wisconsin over the last several years. Two of his photographs were featured in Barnstorm Wisconsin, a touring exhibit of photos on rural life. His photograph, Bear Claw, won grand prize in an Animal Planet contest and several of his photographs were featured in the book, Wisconsin 24/7, one of the state volumes in the successful America 24/7 photography book series. He has also been published in the Wisconsin State Journal, Capital Times, Wisconsin Light, and on several calendars. His photograph of a centipede was accepted for publication in Animal Planet's The World's Most Extreme Bugs, published in May, 2007 and will appear again in a field guide to Pacific Northwest insects to be published in 2011. More than 20 of his nature photographs will also appear in 2011 in a report on climate change in Wisconsin.