Mark Roberts has created a PDML (Pentax-Discuss Mailing List) mousepad that collects (gently tongue-in-cheek, of course) in one handy ready-reference the most common tips dispensed by PDML members for how to improve photographs. Note that all profits from sales of PDML swag go to the National Childhood Cancer Foundation.
While you're there, check out Ken Archer's classic "Photography is simple" quotation, on the middle T-shirt in the top row. It's one of my all-time favorite photography-related quotable quotes.
Mike (Thanks to Mark)