This changes with the ups and downs of society, but circa January 2009:
Based on google’s auto-predicting search features:
Amazon
Best buy
Craigslist
Dictionary
Ebay
Facebook
Google
Hotmail
Imdb
Jcpenny
Kohls
Lowes
Myspace
NFL
Obama
Photobucket
Quotes
Runescape
Sears
Target
Utube
Verizon wireless
Walmart
Xbox 360
Youtube
Zappos
Yeah. How many could we live without? Most.
ADDENDUM: As I predicted, this post received 15+ views since posting; most likely as a result of showing up in search results for the above.
I hate the internet.