I use ix.io with an account set up in .netrc with its command line tool installed; its simple and cool.
Then you can either pipe stuff through it like the above answer:
command which produces output | ix
or directly paste a file:
this returns the url.
Then I additionally set up a git alias for this so that I can easily paste my format-patches and get an url for it:
post = !sh -c 'git format-patch --stdout $1 | ix' -
To paste a patch I do, for example:
git post HEAD~1
or to paste whatever is in your current buffer in vim:
:w ! ix
for uploading files, not too big: http://paste.xinu.at/ with its client.