If you happen to be a Google Voice user and running CyanogenMod there is now a way to have all your messages delivered through the stock messaging app. Or for that matter, have those Google Voice text messages delivered to the third party messaging app of your choice. This method has been detailed by Koushik Dutta of ClockworkMod fame and doesn't appear to be all that difficult to setup.
As mentioned, you will need to be a Google Voice user to start. For this the Google Voice app will need to be installed first with notifications enabled. You will also need to be running a recent CyanogenMod nightly build (July 1st or later). Assuming you have these two requirements already set and in place, you have the hardest part already completed.
From here you will need to install an app called babel-signed. According to the details shared by Koush, you will need to push this apk to /system/app because an adb install will not work as the app requires system/signature permissions. Once that is installed you can start the Babel app, choose Google Voice and then authorize it.
After that has been completed you tap the Accessibility Service button which will take you to the settings to enable the Babel app. That completes the process. For those looking for the simple explanation as to what this actually does;
"The app will sync your existing Google Voice messages into your messaging store. New Google SMS will be received as if it were a normal SMS."
On the flip side, users will also be able to send messages from that same messaging app and have them shown as being sent from your Google Voice number (as opposed to your regular telephone number). Koush also pointed out that 'Babel' will not be the final name which brings the last point -- this is all still a work in progress.