MSN has just switched to web-based email.
But there doesn't seem to be an http option in server types of the mac
version of Outlook Express (or Entourage).
Does this mean I'm going to have to log into Hotmail to get my emails from
now on?

That can't be true. I have an MSN account and it uses POP3 for mail. I do
believe if you are using MSN Explorer on Windows that your mail accounts are
web-based mail. Maybe you can call support and ask them to turn your account
back to POP3?

Outlook Express for Mac can only access MSN Hotmail accounts.  For MSN

Hotmail.com, through Webmail.  MSN Internet Access customers may be able to
access their e-mail through Outlook Express using POP3, but I'm not 100%
sure.    I got a MSN mail account on a Windows computer using MSN Explorer 6
but can only access it on my Mac (the computer I use more than 95% of the
time) at Hotmail.com.  That's why I use Mac.com as my primary mail server.
    Maybe the next version of Outlook Express will have support for other
HTTP servers.