A lot more websites are somehow having playable videos through the iPhones quick-time player. This means the videos no longer have to be that shitty Youtube quality, you can simply click on a video link from Break.com, MetaCafe, GT and a bunch more.
Another great application is called TruVeo. It searches through dozens of websites which provide videos depending on what you search for. For example, if you type "MLB Highlights" in the search field, you'll see lots of your results being linked directly from MLB.com The videos load up very fast, too.
Also, if you put two iPhones next to each other while one uses the Youtube app against the TruVeo app, search and load the same video, you will see an extremely major difference when it comes to visual and audio quality. This program is a must.