There are a few codec packs available, but none as well done as ffdshow. The biggest problem with codecs - or installing codecs one-by-one, is that they tend to step all over each other. With ffdshow, this problem goes away. Another handy feature is the ability to plug direct show codecs into VirtualDub on installation.
Check out the ffdshow-tryouts by clicking here.
Since its open source, check the site often for the latest version.