Because the primary purpose of the internet is to entertain us, right? The internet is the collective intelligence of the human race. All we need is an AI interface and let the fun begin :-)
Homestar Runner
Check out SB emails.
BBC - Doctor Who - The Classic Series
Animations and eBooks free from the BBC
Games
Free online games! w00t!
Comics
Because who can't use a little comic relief?
TV
Yeah, I hate it. It rots your brain, but sometimes that just what the doctor order. At the very least don't pay for it. If you have high speed internet access networks are putting enough good shows on that between them you should stay entertained.