daisy_gamgee has a Merry/Pippen saga (very WIP), which I believe is all archived in a journal,
history_of_us. On the info page for that journal, there is also a link to a website where the story is better organized.
Most of what she has written is M/P, pre-quest, starting with Pippin's birth and moving forward. She also writes some truly excellent, though incidental to the main story, Frodo/Sam. But she has written a few pieces during the quest, and I believe quite a bit of post-quest now, that I haven't caught up on.
Very, very good, if you like pre-quest Shire. Though if you know you like pre-quest Shire, I'm sure you've read it already. :p Her Merry and Pippin are wonderful, and the way she realistically deals with their age difference is very good. Very plotty. And once she gets them past Pippin's "old-enough" birthday, some hot porn, too. ;P
Love THOU! :)