ETA: When you sign up, you will be able to make 3-4 requests, for those who are new to Yuletide!
If you want to leave either the text of your letter or a link to a letter that you've posted elsewhere, please comment to this post with your signup name (your AO3 account name/pseud) in the comment subject line. Writing a letter is in no way mandatory, but such letters can be valuable to whoever receives your assignment, not to mention those who might be prowling about looking for early inspiration for Yuletide Madness.
Note: it's helpful if you include your requested fandoms in your comment, for those people who might consider writing extra treats, or people browsing just to see who else likes their small fandom!
Past years' examples can be found
here,
here,
here, and
here, if you want to see how others have done it!
I'll update the link to this post in the sidebar here and at
yuletide_admin for easy finding.
ETA: And
go here for a link to the handy-dandy spreadsheet of compiled letters that the awesome #yuletide channel has put together, as well as some hints as to help out when posting your letter.