The "kj" remapping seems like a nifty trick; I've spent a while getting accustomed to ctrl-[ instead of the <ESC> key (I can't reach the <ESC> key without moving my left hand), but it's still hard for me to do quickly and reliably.
Another trick that is useful for people who compulsively hit the Ctrl+s keybind from other editors; the following is from my vimrc:
" Map Control+s to save a file
nmap <C-s> :w<CR>
imap <C-s> <ESC>:w<CR>
This leaves you in normal mode which is usually what I want when I hit ctrl+s.