Does anyone know of a recipe for frosting that isn't terribly sweet like buttercream? I want to make cupcakes with those large swirls of frosting on top, but the last time I made them we had to scrape off half the frosting because they were too sweet.

A local cupcake store makes the cupcakes with the large swirls that are almost like a whipped topping (think cool whip) mixed with buttercream. They are just slightly sweet and not over powering Their cupcakes are not refrigerated though, so I don't think the frosting has any dairy products in it.

Any suggestions?

A product called Frosting pride, its a non dairy whipped topping. Comes in liquid form in the freezer section of stores like smart n final, hth.

The most delicious, fluffy, buttery but light, not too sweet frosting I've ever tasted is Swiss Meringue Butter Cream. I watched the tutorial and used the recipe from www.dyannbakes.com.
I have never been a fan of frosting - even though I love decorating with it. But when I made SMBC, I was hooked!!

Would Rich's Bettercream be what I am looking for?

Rich's Bettercream would definately fit the bill. Light, pipes great, non-dairy, just like whipped cream but better - more like ice cream..... See thread Bettercream Fun by Melvira.

Have you considered making your usual Buttercream, but adding another flavor instead of vanilla to it, like Lemon maybe? Still sweet, but with that added flavor, not overpoweringly so.

I made the mock bettercream recipe this weekend and it was perfect. I piped large swirls of icing on top and they looked great and tasted even better. I added crushed oreos to half of the icing and caramel sundae topping to the other half of the icing.