MSI's Afterburner has a tool called RivaTuner which is easily the best solution for AMD/ATI. If it's a pre-HD2xxx card you can skip Afterburner and just use an old standalone rivatuner build. The biggest advantage to both of these tools is that it completely avoids running in the "Driver Test Mode" which opens your system up to a far wider array of malware, virii and other attacks. Not that your AV
won't block them, it just may have to work harder.
Anyway, to configure afterburner/rivatuner to limit the framerate:
When afterburner is running it will add 2 icons to your system tray, one of which is the On Screen Display Server
Open the OSD server (or the rivatuner configuration tool if using rivatuner as a standalone)
Click on the wrench in the upper right corner to get into the Setup options
The initial window should be the "General" tab.
If you are running a post-process injector (ENB, RCRN) check the box for "Enable compatibility with modified Direct3d libraries"
Set the desired max framerate in the "Frame Rate Limit" box. 0 = unlimited, btw
Click OK, then MINIMIZE the tool. Closing it will actually terminate the program.
I think Afterburner will restart it, but you'll have to check the systray to make sure.
I believe this will work even if you aren't using Afterburner's OSD function, but if it doesn't you can configure Afterburner to run the OSD without actually displaying anything.