I'm using Battery Widget it offers a widget and a status bar icon. The icon can show a couple of different things like percentage, time remaining, etc.

Works pretty well, fairly customizable. Gives an estimate of remaining time for usage or time to charge to 100% based on current use (over the last 15-20 minutes). The free version will occasionally pop up when connecting to a charger, you can get a key file for about $1 to prevent that.

I don't have anything running CM, so your mileage may vary, but I've been happy with it / find it useful. Using it on my Vibrant currently.