I'd promised to do a post on boots for those of us with wide calves - but darn it if YouLookFab hasn't beat me too it!
Are Your Calves Too Wide for Long Boots?
Other sources of wide calves boots:
Jessica London (Through not as many as you might think for a plus-sized focused retailer.)
Lands End (Okay, it's only one pair - but they are a great looking pair of riding boots so they definitely rate a mention!)
Lane Bryant (Ladies, these boot are just fierce lookin'! Growl!)