Hi,

I had to do a bit of searching here and there to get emacs running on N810 so I leave my note here for record.

A) You'd need to have root access. I did it by installing SSH server and SSH client then
ssh root@localhost

B) As emacs package is huge (mine is about 80MB including some site-lisp), you'd want to particition the internal memory card to FAT32 and ext3 so that you can store emacs and associated files to card and make symbolic link to it.

I followed instruction in this page to partition and format the internal card:
http://www.zimbio.com/Free+and+Open+Source+Software/articles/77/Extended+root+partition+N800+OS2008

in my case, I splitted the internal card to 1GB for FAT32 and 1GB for ext3. So cylnder was something like this
/dev/mmcblk0p1 : 0 30719
/dev/mmcblk0p2 : 30720 30720
(cannot remember the exact number I used... I entered bigger value in the 2nd argument of p2 then just typed the maximum available cyliners the error message told me)

Somehow mkfs.mdos /dev/mmcblk0p1 didn't work so I used mkdosfs -F32 /dev/mmcblk0p1 or mkfs.vfat -F 32 /dev/mmcblk0p1 instead (I don't remember what exactly I did...)

I followed Step 1, Step 2 but didn't do Step 3. It seems accessing from PC via USB is working fine to me without Step 3.
Hold the Step 4 for later

Reboot and type df to check that /dev/mmcblk0p2 is mounted as /extfs

C) Now the best part. Download emacs and install. I found it in this post.
http://www.mail-archive.com/emacs-or.../msg04697.html
Download local.tar.gz and copy it to /extfs
Then do
tar zxvf local.tar.gz

D) As the Step 4 in A), delete original /usr/local and make symbolic link from /extfs/local by:
rm -r /usr/share
ln -s /extfs/local /usr/local
(well, I think I had to delete sub folders of /usr/share one by one...)

E) You'd want to add /usr/local/bin in your PATH. Create /home/user/.profile file with this line
export PATH=$PATH:/usr/local/bin

Now you are ready to go!

I installed howm mode which is (almost) all the reason for me to install emacs on N810...

Thank you very much Daniel for making emacs available! Thank you mpeters for great instructions!