Android Terminal Editor - nano

Download nano:

Unzip the file and place nano on the root of the sdcard (i.e. /sdcard/nano)

Open up the terminal and enter

$ su root

# mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system

# cp /sdcard/nano /system/bin

# chmod 755 /system/bin/nano