For camera stores, there's two fairly close together, not far from downtown:
http://www.donsphotoequipment.com and
http://www.competitivecameras.com
Depending on if the weather is nice, the Dallas Arboretum is a nice place to photograph:
http://www.dallasarboretum.org
The Arboretum sits at the edge of White Rock Lake. At the north end of the lake, off Mockingbird Lane and near Buckner Blvd, I have shot many a roll of film, and got a few keepers.
Downtown Dallas has a few spots worth photographing, such as the old red courthouse and Dealey Plaza.
http://en.wikipedia.org/wiki/Dealey_PlazaIf you are at Dealey Plaza, you might also enjoy a visit to the Sixth Floor Museum, which is about the assassination of JFK. Sounds hokey, but I found it very educational. You cannot take cameras inside, but when I was there they had the cameras on display that were used to photograph the events around the assassination, and biographies of the photographers.
If you like nature photography, there is
http://trinityriver.audubon.org. It's not fantastic, but a good place to get in an easy hike and see flora and fauna.
If you want to do street photography, there is Uptown Dallas. I don't have a link, but ask a local. It is about the only place in Dallas I am aware of where you can actually see enough people out on the street to make it worth your time.
So that's some outdoor spots. TXForester mentioned good indoor ones.
Happy shooting!