Things to consider
How you decide to thank your volunteers can be as important as the decision to thank them at all. It will informed by many factors; how many volunteers you have, their physical proximity to you and the culture your charity has decided for itself.
Where and how to say it
You should always tailor your thanks to the individual volunteers. A very public expression of thanks, be it in a report or at a special event, may help to carry weight. For people who are uncomfortable in the limelight, a quiet pat on the back, an email or a telephone call, may be better. Volunteers often feel more valued simply with regular contact.
Some organisations choose to present certificates to recognise length of service or hold local events to thank volunteers, especially during Volunteer's Week.
Acknowledgment through words, either in public or private should always be the first port of call. On occasion though, such as the departure of a long-serving volunteer or a significant accomplishment, you may feel that you would like to make a larger gesture in the form of a gift. As a general rule, the act of giving should always outshine the gift itself. Inexpensive merchandise such as certificates, mugs or t-shirts often do the job. Volunteers committed to your cause are likely to be upset if they feel gifts were too lavish. They want to see the resources put into the cause you are all working for.
Charities should always be cautious that, in rewarding volunteers, they do not compromise the legal or financial relationship they have with them. It is good practice to not offer anything of significant monetary value, and not to offer gifts on a regular basis.
See more on managing and retaining volunteers