If your lisp-indent-function is set to common-lisp-indent-function you could try something like:
(put 'let 'common-lisp-indent-function '(&lambda &body))
If you use another indent-function you may need other parameters. For very complicated syntax, like loop, you may also specify your own function like:
(put 'let 'common-lisp-indent-function 'my-indent-fun)
Thank you! This did the trick.
For those who use xemacs you will need to grab cl-indent.el from a recent GNU emacs release and use that instead of the rather old version from xemacs...
-Ram