vi e d i t o r
A nice introduction tutorial in using vi: vi intro -- the cheat sheet method (tip: register for free, then download the PDF).
Two key vi websites are The Vi Lovers Home Page and The VI Pages.
There are many versions of vi: vim (http://www.vim.org)
is very popular and has a number of extensions that make vi a lot
The vi manual pages in the AIX Documentation Library may also be of help.