You could do this one of two ways:
1) Use a URL that includes some sort of individual entry marker, i.e. the hhmm that it was posted, or the entry ID, as the directory name and use index.html (or index.php or whatever) as the filename. (I use the entry id on geeksblog, and the URL in MT looks like this:
http://backlog.geeksblog.com/yyyy/mm/dd/entryid/index.phpbut you can type
http://backlog.geeksblog.com/yyyy/mm/dd/entryidto get the same thing.)
2) URL rewriting. This would be a really simple way of doing it as well...simply create a file named .htaccess and put it in the base directory where your achive directories are, with this in it:
RewriteEngine On
RewriteRule
+)/([0-9-]+)/([0-9-]+)/([a-zA-Z0-9._-]+)]http://([a-zA-Z0-9.-_]+)/([0-9-]....9._-]+) http://$1/$2/$3.htmlYou'd put your files in directories as such:
http://site.tld/1/2/31 - any numerals and/or the dash character can go there (the entry date in your example URLs)
2 - any numerals and/or the dash character (the time in your example URLs)
3 - the entry title, dirified - any numerals, any characters a-z and A-Z, and the characters . - and _ can go there
(untested but should work - let me know if it doesn't)
Doing it this way, you can name your entry files topic_title.html but the user can type the URL without the .html and will see the correct page (and the URL he sees in his address bar will not have the .html).
3. Assuming your server will parse a non-directory file as HTML, just don't give the files an extension and the URL looks clean without any bother.