Donald Abrams' FDA-approved study on cannabis and HIV patients ... which found that marijuana didn't make the disease progress, was effective in treating wasting syndrome ... and although it wasn't proven beyond a shadow of a doubt, the patients who smoked marijuana experienced a decrease in HIV RNA numbers.
Other studies, most of which are international for obvious reasons:
http://www.cannabis-med.org/studies/study.php***
(** On Edit: I didn't include this one, which is official but still on the anecdotal side:
http://www.nap.edu/html/marimed/ . And let's not forget the studies Nixon commissioned ... which found that recreational marijuana use was not dangerous enough to warrant prohibition).