is there a pastebin service that supports terminal escape sequences?

Termbin.com supports what you need.

$ grep --color=force foo /etc/motd | nc termbin.com 9999
http://termbin.com/xxxx

$ curl http://termbin.com/xxxx

You'll get exactly what you sent.

The service is running on a free and open software called Fiche so you can also install your own.

pastebinit isn't satisfactory.

You can convert ascii/ansi to HTML via the 'aha' (ANSI HTML Adapter) command.

sudo apt-get install aha || sudo yum install aha
ls --color m* -d | aha

Unfortunately - you can't just pipe that HTML into pastebinit. You could host the HTML temporarily if various firewalls permit it:

mkdir /tmp/temphosting
ls --color m* -d | aha > /tmp/temphosting/cmd.html
cd /tmp/temphosting
python -m SimpleHTTPServer

Then point a web browser to http://ip.or.host.name:8000/cmd.html

There is actually a new service I just found out about called asciinema.org which provides on-screen recording facilities. It is not a pastebin, but it is probably the best approximation of what I was looking for.