If you don’t know already, SmartThings has a preliminary list of devices that they know work. You can find the list here: http://build.smartthings.com/compatible-devices/
However, there are also a number of devices that users have had success with that aren’t on that list. Obviously these aren’t officially supported so even if some of us have them working great, there isn’t a guarantee that they will work for you.
If you do add something to the list here, please try to provide a link or at least some detailed model number info to make sure that others know exactly what device you’re talking about.
I, personally, have a couple of Intermatic devices:
HA01C - In wall outlet. Top outlet is switched, bottom is always on. Works perfectly. I have two in my garage that I use with relay as garage door openers.
HA05C - Screw in module. You screw it into a light socket, then your light into this module. Says it can control CFLs as well as incandescent. Only on/off. Works perfectly with ST.