You can watch all episodes of Gossip Girl with an FLVDirect player.
Just get any FlvDirect player
ex:
link (it´s a free one)
1. click on -> search -> video
2. search for "Gossip Girl all ep" (they´re online, i searched a minute ago)
3. choose from list & click on -> watch online or -> download
enjoy
(If you search for a certain episode of a tv show just add "all ep" to name in the search field and you will get all episodes listed)
PS: you can also search for movies,tv shows, musicvideos etc etc