Unfortunately this function usually only works in the USA. I tried watching a few episodes over here in Germany, but unfortunately I am blocked from the network.
What does ABC offer? Currently on their website, they are streaming full episodes of Grey’s Anatomy, Desperate Housewives, Lost, and Ugly Betty. The stream, for those who can view it, is shown in good quality and also cuts out most of those annoying commericals shown during its prime time showing.
Another good site to watch some full length episodes is on Comedy Central’s website. Here they stream clips and videos from almost all of their shows. Now you can always get your daily dose of John Stewart and the Colbert Report.