I'm finding the Mrs. Pollifax series to be very, very funny and reminiscent of the Miss Melville series. Instead of a spy like Mrs. Pollifax, Miss Melville is an assassin! She was actually trying to commit suicide by shooting herself but...well, she missed!
Long out of print but I see the first four books in the used bookstores all the time. The fifth and last book in the series, on the other hand, I'm still trying to find!