Buzz Player HD hands down $3.99...look no further. I also use Airvideo....but what I like about this is you can download to your ipad, iphone, etc...
If you share your folder on your computer, there is a button to download over wifi with SMTB file sharing. On my wifi you can get a 700mb AVI in about 10 minutes. I particular love this because then I can easily bring a few movies for the plane. It will also stream to Airplay, but I use AirVideo for that. And if you haven't yet get an AppleTV. It is worth every penny to stream from your mac.