Today valgrind 1.0.1 was released. It's a pure bug fix release. The dev-util/valgrind-1.0.0.ebuild still works, it just need to be renamed to valgrind-1.0.1 and a new digest file needs to be created.
*** Bug 7546 has been marked as a duplicate of this bug. ***
*** This bug has been marked as a duplicate of 7546 ***