There was just a groupon, I think it was $20 for a regular, 15-month membership. It was for new members only, so I didn't look too closely.
I have the credit card, but only use it at Sam's. Also, the Plus membership is worth it to me, just for the earlier shopping hours. I'm a morning person anyway, and the Sam's location isn't very convenient--traffic gets heavy later in the day. YMMV, of course.
P.S. My DS10 came home with one of those coupon books that the PTA is selling. It had $20 off a new Sam's membership, $10 off a renewal. It's worth taking a look, if you have those books available to you.