Placing an acknowledgement in a local or national newspaper is a good way of thanking all those people who have supported and helped you through such a difficult time. This can be arranged by your funeral director.
If you did not put a notice in the newspaper before the funeral, you might wish to consider this now, in memory of the deceased and as a ‘thank you'.
Alternatively you could call or write to people to whom you are particularly grateful. Many funeral directors can supply printed acknowledgement cards if you do not feel you can manage individual letters.