I generally use the php method for this, as it allows my wordpress directory structure to stay intact, and later if I want to add a regular old site with its own homepage and a link from it to the blog I can without having to change the wordpress installation at all. Here's what I do... create index.php and put this into it:
<?php header("Location: http://whatever.com/wordpressdirectory/"); ?>
Make sure there are no other index pages in your root directory and this will do you up wonderfully.
"Whenever you find yourself on the side of the majority, it's time to pause and reflect." - Mark Twain