$ curl -L -v -F "value=@myfile" "http://domain.tld/whatever.php"
Feb. 15, 2012, 11:26 p.m.
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openiduser14
Explanation
curl
read "man curl" if you need to info like using cookies,etc. you can also use wget
-L
follow redirects
-v
be verbose
-F
an input field
value=
the name of the input field
@myfile
the file you want uploaded
"http://domain.tld/whatever.php"
the url that will take the file