I have many camera bags, but none of them would fit my iPad. I researched into many mainstream camera bag manufacturers, and I discovered that Lowepro, Crumpler, Kata and Domke did not make a medium size should bag that could contain my 5D MkII and an iPad comfortably. However I stumbled upon the ThinkTank Retrospective 20 that does fit an iPad and a pro size SLR or two. At the time of writing Think Tank were sold out in the UK, and I am pretty sure I got the last one. This bag is by far the best camera bag I have ever owned, and maybe this will be the last bag I buy (I won't hold my breath).
Here is a review for the ThinkTank Retrospective 20; but if this is too big for you, then you can go for the smaller ThinkTank Retrospective 10. The Think Tank Urban Disguise 30, 35 and 40 will also fit an iPad, but I don't think they look or feel as nice.
