I have published a post How  to ban IP address (click BACK button to  get back to this page) and in its original version, tested to  work. However, I do not have any IP address I would really want to ban,  so didn't implement it for any of my own main blogs. However, a blog  visitor commented that he couldn't get to the original site I used to  generate the code to ban IP addresses. I checked and it was true, so  added an update. Later, that site went offline, then online, then  offline. I had to put up more than one updates. Then another blog  visitor commented that that the site is online, but goes to a different  address. The new address is
http://www.toolator.com/
Apparently,  the site owner or owners have added more applications, of which IP ban  is only one. You have to click on a link "IP Address Blocker" at the  above site to get to
http://www.toolator.com/generators/ban/
This  is the screenshot from the above site, after I have added my own IP  address to ban so that I can test:

If you  click on the above screenshot, you will be able to see everything more  clearly, including very faintly, my current IP address (mine is a  dynamic IP address, which means it is not the same all the time. I may  get another IP address if I switch off the modem, switch it on again to  get back online) which is displayed faintly in red beside "Don't ban  your own IP address:" My current IP address is
60.49.68.218
Today,  I got another comment, asking how to add the URL to redirect the  person(IP address) we want to ban. As I haven't tested the new site yet,  I decided to test for my own blog 
Natural  Remedies. It didn't work. I went to
http://ipchicken.com/
to  reconfirm my current IP address, and it was reconfirmed that the above  IP address is my current IP address. If you want to check your current  IP address, copy the above URL and paste it into your browser address  bar (preferably in a new tab with a browser like 
FireFox  so that you do not need to lose this page.
I decided to test it  for another of my blog 
Health  is Wealth, and reconfirmed it didn't work.
The above 2 blogs  use the New Blogger template, so I decided to test it on a blog 
Blogger old classic template store, added it direct  to the template rather than through the LAYOUT as in the cases above,  and it still didn't work.
I will have to do some further checking  and will either add an update here or do a new post plus add a link to  that new post here if there is any fresh development.
BTW, the  latest question from the blog visitor was how to add the 
URL to redirect the person (IP address) we want to  ban. (The IP address ban is not an actual ban but a redirect to another  site that we ourself can specify). The original test was done a long  time ago, so I cannot remember exactly, but vaguely remembered there was  a way to add the URL of the site we want to redirect traffic from the  IP address we want redirect to. However, when I did this test, there was  no way for me to do that, so I assumed that the site to be redirected  to would probably be that of the application creator. But as my test  showed, it just didn't work. So you just have to be patient while I try  to work this out.
In the meantime, if you happen to be reading  this post and want to ban an IP address or you want to test it for  yourself, I would very much appreciate you let us (me and this blog  readers) know about your experience by adding a comment.
Update 29 October 2007: Got a response from the  creator of this IP Address Ban who says he is having problems with his  current webhost which I will paste verbatim below:
"The next  couple of months I`m going to work on a new system on another webhost.  So I hope to offer somewhere in the month January 2008 a new ip-blocker  service. Maybe with some extra futures."