Suggestions on how to thank your recommendation letter writers

i have yet to write a thank you letter to my boss who wrote me a wonderful letter of recommendation. however, i didn't get a chance to use it because i found out that i got into a program a few days later. should i give her a gift (what kind of gift) or would a sincere thank you card suffice? also, i gave thank you cards to my professors immediately after they wrote my letters. i already told them the good news via email. should i give them another thank you card and a gift as well?