Shops in Prague?

We'll be in the Czech Republic for a few days next week. Are there any good shops I should attempt to "accidentally" pass by?

I assume you mean photo equpiment shops. You can try Foto Skoda (www.fotoskoda.cz) and Foto Pazdera (www.fotopazdera), both in Vodickova street near Wenceslas square. The first sells new and used, the latter only used equpiment. There is also "Bazar Nekazanka" in 17, Nekazanka street that has - among other used things - some used photo equipment. This is not very far from Vodickova street. Google maps will give you an idea, these shops are just a couple minutes walk from each other.

I remember every week-end there was a giant flea market near the football stadium; in 2006 I saw quite a bit of odd large-format stuff, but wasn't interested at the time.
Sorry I can't be more specific, I only went twice.

Thank you both. Although I was in Wenceslas Square, I was not successful in persuading my wife and other traveling partners that a visit to the camera store was absolutely essential :( This was in part due to us having lost a day because of the volcano. Next trip....