That's up to you, and your style of administration. I personally put all Groups in an OU labeled Groups, then I place all Distribution Lists into an OU called DLs.
PSC
Governments and corporations need people like you and me. We are samurai. The keyboard cowboys. And all those other people out there who have no idea what's going on are the cattle. Mooo! --Mr. The Plague, from the movie "Hackers