Is sendmail still used and, if so, for what?

Painful configuration process aside, it's still a perfectly serviceable mail exchanger, and arguably more flexible and configurable than many alternatives. (Just TRY configuring qmail to play tic-tac-toe :D) I've worked on a number of sites that run Sendmail quite happily within the past few years.

For me, it gets replaced with postfix ASAP.

Legacy applications. Just because a CGI web application was built 7 years ago doesn't mean that it needs to be replaced, and if it replies on sendmail, then so be it!

Sendmail is installed by default on FreeBSD :)

In addition to FreeBSD, sendmail is the default MTA on RedHat systems. While it has a long history of security vulnerabilities, it is still the most tested MTA available for UNIXy systems. I have looked for recent figures on MTA distribution (please comment with links if you have one), but as of several years ago it was by far the most used, with postfix (iirc) the nearest competitor.

We're still using it on all of our Solaris systems.

While we are primarily an Exchange shop for end user email, we still have sendmail running on a handfull of *nix boxes. The most common reason is probably because there is an application running on the server that wants a local mail server, we just have sendmail set to forward to our normal outbound SNMP host.

The one big exception is on our monitoring server, where we have sendmail running along with qpage. Sendmail does forward to the normal snmp server for the email notifications but for SMS we're going through qpage so that if exchange goes down or is slow the notifications still get out.

We still use it everywhere because we know it, and it works.