^A - move to start of buffer
^E - move to end of buffer
^U, Shift-Del - delete (clear) buffer
^W - delete word to left of cursor
Left/Right arrows - move cursor

Future plans?

Up/Down arrows - history (if we can spare the RAM)... OR:
Up/Down arrows - move up/down by one line (40 chars)
^Y, Shift-Insert - paste (^U and ^W fill a paste buffer)
Ctrl-Insert - toggle insert/typeover
Atari key - compose? we don't really have the font for it :(
^U should be "delete to start of buffer", not delete whole line.
^K - kill (delete) to end of buffer.
Ctrl + Shift + Left/Right - move back/forward one word (space-separated).