Here's one I did last July. It's not great, but I had just received my 30D two months prior and had never done a group shot, so I was pretty happy with them. 23 people total and 3 dogs.
Standard pose:
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One more, This is the "goofy" family shot:
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Both were taken with the 17-85mm f4-5.6 and I can't remember if I had the 430EX flash then or not. Exif says flash fired so I'm not sure if that was pop-up (which wouldn't have helped) or the 430EX. Both were taken in partial shade with tripod and using the cameras timer. For those interested, I'm the dork at top left.
Hope this helps. This was the one and only time that I have taken a group shot.