Here is a letter from the Frierdike Rebbe to R' Hershl Shusterman dated 6 Teves 5704 about a range of issues. There is concern for an individual child observing kashrus and a detailed look at the running of Shabbos services amongst other things.
Here is a letter from the Rebbe to Mrs. Einbinder of New Haven advising her to purchase a ready built home and make alterations rather than buy a plot of land and build a new house.
The Rebbe signed the letter in the name of the mazkir.
Here are three letters that remind us of the level of obedience that existed in the earlier years of the Rebbe's nesius. The first letter is a letter from the hanholo of Yeshivas Tomchei Tmimim in Montreal to the Rebbe's mazkirus asking for permission for seven bochurim to travel to the Rebbe for Rosh Hashona 5714.
The other two letters are from Rabbi Chadakov to the hanholo giving permission for two bochurim to stay in NY.
Here is a handwritten copy of the famous bar mitzvah maamer isah b'medrash tillim from the Frierdike Rebbe's bar mitzvah in 5653. In addition, there are many notes in the Rebbe's ksav yad. I'm sure this has been printed before, please indicate in the comments where it was printed. If anyone knows who wrote the hanocho please let me know too.
Here is an answer from the Rebbe to a suggestion to correct an omission from the sicha of parshas Behaaloscho to be included in the sicha of parshas Shlach.
In a letter that was to be printed in "Hamo'or" (dated 13 Iyar, 5741) which read: "מכתב נורא", ("a awe-inspiring letter"), the Rebbe asks: "למה להוסיף בהפחדות" ("why add fright?") , and later corrected it to read: "מכתב מיוחד" ("a special letter").
Sorry for the gap in posting. Here is an unprinted letter from the Rebbe to R' Volf Greenglass dated 11 Tamuz 5716. The Rebbe expresses his dismay that bochurim were sent to eat at the homes of the Baalei Batim and didn't eat in yeshiva during Pesach.
Here is an unprinted letter from the Rebbe to R' Volf Greenglass dated 7th Adar 5715(6?). The bochur referenced in the last paragraph is R' Nisan Mangel and the ksav yad shows us how much the Rebbe appreciates receiving kisvei yad.
Here is a partially printed letter from the Rebbe to R' Volf Greenglass dated 15th Iyar 5714. The first half of the letter is printed in Igros Kodesh v.21 p.260 until 'haseder' and from 'ulechen' is not printed. I deleted the second half of the letter due to it's sensitive nature. The ksav yad at the end is printed at the above location.
Here is an unprinted letter from the Rebbe to R' Volf Greenglass dated 29th Tevet 5714. THere was a fourth point in the letter but I deleted it due to it's sensitive nature.
Here is an unprinted letter from the Rebbe dated 6th Shevat 5713 to someone about the healthcare of their daughter and a demand for information about a certain bochur.
In the past I have attempted to spread posts to get a sense of continuity, however, since I can never know when I will have the few moments to post things I've decided to post as much as possible at any given sitting.