Sprunge this! Sprunge that!

Bash, 30 bytes

curl -F'sprunge=<-' sprunge.us

Just removed the unneeded space in -F 'sprunge=<-' and the http:// from the sprunge.us url. OP gave me explicit permission to golf his reference solution.

HTML, 88 bytes

<form action="http:sprunge.us" method="POST"><textarea></textarea><button type="submit">

To test this easily, prepend data:text/html, to the code and paste it into your address bar (works for me on chrome).

Full (easily) testable code:

data:text/html,<form action="http:sprunge.us" method="POST"><textarea></textarea><button type="submit">