Erect penis size bell curve (ok, it's a bar chart, but I trust that you can visualize the curve... among other things):
Comment sections are ablaze about the recent study that suggest that most men who worry about having small penises are unduly worried:
Almost all patients overestimated the normal penile size. Most men found the combination of sex education with standard penile measurements helpful and relieving. CONCLUSIONS: Men complaining of short penis could be treated using basic principles of sex education with objective methods of penile size evaluation. This combination can correct any previous sexual misconceptions, relieve unnecessary anxiety concerning penile size, and decrease the desire to undertake still-to-be verified lengthening procedures.
My best sex ed class started with a slide show of 100 penises of varying size and health (ew). It was a college class, but this would be a great tool for pubescent sex ed too. The side show wasn't sexy or provocative - in fact the point of it was to desensitize giddy American college students so they could talk about sex without giggling or blushing. And it was totally effective.
Besides the size question, many kids wonder if they look "normal" or are deformed - perhaps because of the derth of images available to them of human bodies. Those line drawings and cartoons just don't cut it. Not all little boys are lucky enough to grow into gay adolescents that get to compare their penises to several (ok many) others, so perhaps a photo slide should could be a helpful tool. This is puritanical America, so it seems like a long shot, but too many little boys learn about sex from porn magazine, with their unrealistic depictions of bodies and sexuality.