Facebook:
lite.facebook.com

Dropbox
www.dropbox.com/m

Google Reader:
http://www.google.com/reader/i/

Google Calendar:
www.google.com/calendar/gp?source=mog&hl=eng

GTasks:
http://mail.google.com/tasks/ig

Gmail:
m.gmail.com

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None of this are compared to the full version, well duh!, of their sites... my point here is just that it isnt because I have a full web browser in my pocket that I want to waste time waiting for stuff to load. Sometimes I just want to check some of my document from dropbox, or search quickly for a message in gmail...

Add some more here