This blog is updated daily.
A general description is here.
load(), save(), dput() and dump() now open a not-yet-open connection in the appropriate mode (as other functions using connections directly already did).
Tags \if, \ifelse and \out have been added to allow format-specific (or more general, using \Sexpr) conditional text in man pages.
The 'type' argument of index.search() is deprecated: there are no longer directories of types other than 'help'.