I didn't see a thread for this, but Lyft (unlike Uber, sigh) seems to have quite a few promo codes all the time for various forms of rides. I thought maybe we could start a wiki or at least a thread for all of them.
The ones that I know of currently are:
GOOGLERIDE- $10 off your ride to/from the airport, can be used 5 times, but only for select airports. They doubled my promo with another $50...Sweet!
Please feel free to add yours.