DrDoc - 8:41 pm on May 9, 2013 (gmt 0)
There's also content negotiation ...
If you simply want example.com/foo.html to look prettier (example.com/foo), then there's no need for redirects. Simply let Apache handle it for you via content negotiation.
Now, like lucy24 said, if there's more to it than that (in addition to removing .html from the url you want to direct your request to a file with a different name, or within a different folder), then redirects may be required.