Are you suffering from writer's block? Are you in need of some inspiration for a topic for your next letter? See if any of these questions spark an idea:
Who have you been meeting with lately? What's happening in their life?
What conferences are coming up? Will you be going solo, with your team, or bringing some local people with you? What do you hope will be the short-term and long-term effects of this conference?
Are you planning any other travel, either for vacation or ministry support? What goals and prayer requests do you have for this trip? If it's just after such a trip, what were some highlights?
Have you recently been to a conference or gone on a trip? If so, what were the highlights? Include pictures!
How does "a day in the life of _____" look? The focus can be yourself, a local Christian (either a specific person or in general), a local non-Christian (ditto), etc.
Who or what can your supporters pray for? If you've mentioned someone or something in a recent letter (or even a not-so-recent letter), do you have an update for your supporters?
What are other members of your team writing about? Avoid copying someone else's letter verbatim, especially if there's overlap on your mailing lists, but it's a good source of ideas.
Have you talked about your ministry's vision or mission lately? Why do you do what you do? Did something happen recently that epitomizes why you are where you are?
How does your ministry vision or mission play itself out in your daily life? How does it affect your point of view as you're walking/driving around town?
Hopefully one of the ideas above will help you come up with a topic for your next prayer letter. If not, try having your own brainstorming session, working off of one or more of the following questions:
What might I write a prayer letter about, at some other time of year?
What might someone else write a prayer letter about, if they were ministering here?
What might I write a prayer letter about, if I were ministering somewhere else?
What might someone I know (name a specific person) write a prayer letter about, if they were in my shoes?
What would I never, ever write a prayer letter about?
Get some thoughts written down, no matter how crazy they seem, and keep going until you have between 10 and 20. As in any brainstorming session, don't judge any idea's merit until you're done. The purpose is solely to get ideas on the table, en masse.
Once you have a list of ideas, then see how you can take one or more of them and shape it into a letter, to ensure that you maintain regular communication with your supporters. Save some of the others for future letters.