I use Mutilate Points for this. It also shows DP applications to the mob.

I have tried a lot of addons for combo points and poison stacks but I always come back to Combo Points Redux it. It is a simple addon that allows you to customize how where and how you want the info displayed. Its real user friendly and always seems to work... I have in the center of my rogue a Number that is displayed based on my combo points and green dots out to the side that show my DP stacks. Give it a try.... Works great for me

If you want a combo points addon that DOESN'T make you want to gouge out both eyes because of its ugliness I'd suggest ccComboPoints...or rather the patch version of ccComboPoints because the original doesn't work.

I use Nugcombo Bars. It can be set up in points with http://www.wowinterface.com/downloads/info6308-NugComboBar.html or made into stripes with the plugin http://www.wowinterface.com/downloads/info15533-NugComboBarStriped.html .

Very configurable and easy to use.

I use Hear Kitty both on my rogue and my feral druid (http://www.wowinterface.com/downloads/info6357-HearKitty.html) which provides audio cues for combo points, so I never have to bother looking for it.

thanks for all the great suggestions. Giving Nugcombo bars a try as it seems like the simplest lowest maintenance option.

thanks again, much appreciated.