Go on Hulu and type 'spongebob squarepants' in the search and you'll fine a bunch of them. Youtube is actually WORST because it doesn't show anything clearly!
Where Can I Watch Free Full Length Episodes Of Spongebob Squarepants?
On youtube its the best place ever
Youtube
Nick.com
Try spongebob-squarepants.edogo.com as youtube will only gives 10 min. Video clips to watch.