It sure sounds like rachael price of "lake street dive."
Her name is Jetty Rae. I heard that song too and found her on itunes. She's great!
Jetty Rae
Ebony Buckle is the actress and singer on the commercial.
Erin McKeown
In the recent ads (2010-2011) the "Sweetness Stories" songs are performed by Therese Hegler.
The voice and violin on Truvia commerials that first aired around 2009 is that of Rebecca Zapen, and she's a violinist/vocalist/songwriter. She mentions the Truvia tv ads on her news page: However, she is not the voice on the more recent singer-songwriter style ads.
Jetty Rae
Erika Davies sings 'Just Wanted You To Know' on the Vistaprint Christmas commercial.
Pomplamoose...
Erika Davies
Santa.
I do not know who sings the 2012 jingle but the person who said Erin Mckeown is incorrect. Erin made it a point to clarify it on her Facebook page. Her twitter account is @ebonyrosebuckle