I had an interesting little idea on how to view HTML files on my desktop web browser, even though I'm running mutt through SSH!
I put this in my .mailcap: text/html; opera %s "opera" is a simple perl script to rename the attachment to a value that is guaranteed to be unique (<time>_<pid>.html), invoke "sz" on the file (using the ZMODEM protocol to send the file to my computer, since my ssh client supports ZMODEM), and then print a special string that gets picked up by a trigger in my SSH client, which invokes my web browser to open the file. So, just by viewing the attachment in mutt, I can have it show up on my web browser, over SSH. I found this trick to be more interesting than useful, though; I rarely have a need to view bloated HTML e-mail. It's also a bit slow.