Ive made Qoop calendars two years in a row for ourselves and for gifts, and the quality and detail are awesome. Qoop also works instantly with flickr, if you use that for photo hosting - a nice bonus for designing instantly! Another cool thing is that when you upload photos and choose other details, you can opt for US or other international holidays, so it's very customizable.
My one piece of advice from making two years worth of calendars is that lighter photos seem to reproduce better than medium/dark toned images, so Id suggest erring on that side of things when choosing and editing your pictures for print. Heres one of my favorites from last years calendar we went on a family trip to Eastern Oregon and I snapped this photo of my daughter Pearl in a covered wagon at the Oregon Trail Interpretive Center.
Prices start at $20 at qoop.com