You don't say if you mean websites for students or for teachers ??? If you mean for teachers - with lesson plans, methodology, materials for classroom use etc, the best are often the publishers, which provide a wealth who provide a wealth of supplementary material for use with their courses - but which can equally well be used without using the course. My favourite is
OUP - if you go into their section of business English books (the link takes you straight there) you'll find loads of material, including the tapescripts and texts from their books, which are eminently usable even if you don't have the books and tapes themselves. See
here for an article on how you can use them. You need to register for the OUP site, but it's free.
Other publishers with some stuff :
Macmillan - and in particular their site for teachers
onestopenglish, and
Longman.
Other good sites include :
English club - business English
and
The BBC Learning English site
You might also think about joining the
IATEFL Business English Special Interest Group - they send out monthly newsletters with teaching ideas, articles etc.
Hope you find these links useful.