It just depends where you are... if you're already in a thread you posted to, then Dave's suggestion is quicker than going back to the main page to click the "recent posts" link.
However, if you're just coming to the forums and the first thing you want to do is check for replies in threads you've posted to, then OuT's suggestion is quicker than first finding one of your own posts.
BUT... the
quickest way to find your recent posts
regardless of where you are, is to create a shortcut and put it in a Windows toolbar.