Over at the LJ Yuletide community, someone is assembling a spreadsheet of Yuletide letters and fandoms. It's my understanding that leaving a comment with a link to one's 'Dear Yuletide Writer' letter is completely optional.
However, if one does choose to leave a comment with a link and a list of fandoms, people seem to be using the links and spreadsheet to browse the letters for fun and find interesting letters for which they'd like to write treats. :)
edit - "Please remember to include your signup username in the subject line (especially if it's not the same username as the journal you're using to post here). :D"
yuletide: Dear Yuletide Writer 2011 (collection post)
However, if one does choose to leave a comment with a link and a list of fandoms, people seem to be using the links and spreadsheet to browse the letters for fun and find interesting letters for which they'd like to write treats. :)
edit - "Please remember to include your signup username in the subject line (especially if it's not the same username as the journal you're using to post here). :D"