Try out JS-Kit its very easy to implement and send you an email every time someone leaves a comment which is cool. You will need to add it to your custom theme entry. take a look at the link bellow to see what it looks like on my blog:
Just wanted to add my support for Diqus too. It is very simple to implement. What I like most is that I can run my Shared News feed from Google Reader, through Tumblr and enable comments on those items (and other Tumblr posts as well or course). In theory I think the possibilities for having a conversation about things that have my attention are exciting - but I have yet to find anyone in the world interested enough to leave a comment (guess I need to work on being more interesting!). http://iconolith.tumblr.com
Permalink Reply by Dan on March 27, 2008 at 2:58am
I don't understand why they don't just implement a comment feature, perhaps they will soon. I know that people don't like comments but a simple switch comments on/off would get past that.