What I've been doing with my 3.5 orphaned credits: take an occasional WN flight, and put rental cars and hotel stays on my RR account. I've gone up to 7700 points (out of 15000 needed), so I am on pace to make it before my first credit expires in June of next year.
I will also sign up for Rapid Rewards Dining.
http://www.rapidrewardsdining.com/bonus.htm
You can earn 300 bonus points just for signing up and dining somewhere (if you spend at least $25 in 60 days - easy to do!). As I understand it, these points are in addition to any points you earn in your credit card program (cash back, etc.) so there's no reason to not sign up for this. I was hesitant to sign up for a long time because I didn't want to lose my cash back bonuses and stuff, but apparently you don't lose anything. I'm not sure whether there's a restriction that the RR account and CC account have to be under the same name, but if not, the person who posted that his/her daughters have orphaned credits could put one of the daugher's accounts under his/her own credit card to earn them some points (if the daughters are not yet old enough to have CCs themselves, otherwise, encourage them to sign up).