The most obvious ones to take note of that they can impair judgement/concentration, hence if someone is affected they shouldn't be driving or operating jack-hammers.
Some sedatives can also be longer acting- The consequence of this is that potentially they can affect you the following day as a "hang-over" effect. In elderly people, for example, they can be prone to falls (breaking hips) as a result.
as bafana mentioned, there are different strengths...
xanax/kalma (alprazolam) - shorter acting
normison/temtabs/temaze (temazepam) - also short acting - approx 8 hours
murelax/alepam (oxazepam) - short acting
valium/valpam/antenex/ducene (diazepam) - longer acting
mogadon/alodorm (nitrazepam) - longer acting
rohynol/hypnodorm (flunitrazepam)- very strong/long acting
Here's a consumer medication for ducene (diazepam) which lists common side effects that you can get with any of the above medications.
http://www.mater.org.au/pharm/HealthLin ... ch='ducene'
Note, the stronger the medication, the more likely you are to experience these.
Also, there are other types of over the counter medications (in some countries) which contain antihistamines and the like to promote drowsiness. These have OTHER side effects as well which include impairing memory in certain people, such as elderly who are already forgetful, they can affect blood pressure, vision, bladder/bowel function amongst others effects....