One of the features I really like on Steam is that it tracks your current and total time played for any given game. However, I've not come across any applications that let you do this outside of Steam, apart from XFire.
The problem with XFire though is that it does not seem to let you add your own games, and it doesn't automatically detect GoG games.
I would like some way of tracking playtime with GoG games (and other non-steam games) relatively easily, and I'm too lazy to just note down the times and keep adding up. Automation is key here.

Would be fun, but don't hold your breath.
The only way to get this would be a community-esque program to run in the background. You know, like Steam, Impulse, and XFire :p
Maybe the mythical update to the site will take it a step closer, but it will probably be a while until GoG jumps down that rabbit hole.
As for XFire: You can add the GoG games, you just need to make sure XFire has the game in its catalog. Then you just go to the options menu (been a while since I used XFire), go to detect games, then scroll down to undetected. Then manually find the executable for the appropriate game.

I wasn't asking for GoG to add support for it. I was asking for an existing application that actually does it.

And the answer was XFire.

Xfire doesn't do ScummVM or DOSbox games at all as far as I can discern... it may work for such games sold and run through steam.

I see no way of adding custom entries to XFire.

This isn't game oriented and will still not really be able to distinguish between dosbox games (unless you use multiple installations) and may not be free (seems to have a trial and full version), but
http://www.neuber.com/timeanalyzer/

Hmm, I do seem to have been mistaken. It seems you can only manually add games that XFire already supports, but for some reason doesn't detect on its own. So if the GOG game you want to add is supported but not detected automatically, you can add it manually.

Is there any reason you can't manually add the games to Steam? All the ones I have added still seem to get their time tracked, at least locally (not sure if it reports that stuff to the community).

There is a time management program I use called Rescue Time. It's not meant to track videogames per se, but it would work. It keeps track of every program and website you use and gives you printouts of how much time you spent using each. You can back track and get readouts and graphs about how you spent your time on your computer for the past days, weeks, months, or years.
You can also set goals for how much time you want to spend (or not spend) on something and try to meet those goals. It will send you e-mail notifications if you met your goals.

Why didn't anyone mention Raptr? Does exactly what you want... provided you have it running.
And it recognizes the game, which it tends to do.

Doesn't seem to quite work, I can add games and it detects me starting them, but doesn't seem to track the time. This was for dosbox games run through the GOGWrap utility. Also there's no way to launch the game from within Steam, I have to do it from outside.

This looks sweet. I'll check it out.

Join our Raptr cult...BWAHAHAHA...err...uhh...join.

I'm on Raptr as well. Finds games better than Xfire that's for sure, plus you can integrate Xfire, Steam and GFWL is you want as well.