Thank You letter?

Is it a good idea to send a thank you letter for an interview? I think I had a decent interview last week. Although its only part-time and working at a jail, it would probably be good experience. She said she would let me know by the end of this week or the start of next week. I do have some other apps out for full-time positions, mostly at nursing homes. I really don't want to work at a NH, but need the FT hours or I will have to work 2 PT jobs. I have'nt heard from any of them so far though. By the way the interview was last thurs.