I like http://www.hulu.com
since their videos play flawlessly with a default Mint 5 install. Granted, the selection is quite small, but everything works with no adjustments necessary. This could be an option for those who do not want to fiddle with tweaks or installing WINE.
I am sure there are other sites such as Hulu, but I have not gone hunting for them yet. It could be a good idea to keep a list of sites that simply work, those that work with tweaks, and those that work with WINE. It might be a summer project for some of the videophiles. Anyone care to share what he or she has already uncovered?