Leaving the batteries in your camera for a week or two between uses will be no problem. If you plan to leave your camera unused for six months to a year, you might want to take them out.

And, the lithium battery pack used in your camera (like most current dSLRs) should hold its charge on the shelf fairly well, so you won't have to worry too much about it being drained just sitting there.

(If you do need to shelve it for a long time, the battery will be best if stored at a little less than half full.)

A few references for further reading: Tektronix's Lithium Ion Battery Maintenance Guidelines and Ars Technica on What is the best way to use a Li-ion battery?.

Some rare cameras may have problems where the battery is drained by the camera even when the camera is off. You'll know if you have one of these by whether your batteries still work after two weeks. In that case, there's still unlikely to be any actual harm; battery life might be shortened somewhat, but not more than it would be by actual heavy use.