(1) I see your post at Techorati: "www.keotag.com is a Godsend for wordpress .com bloggers. This site will automatically generate all the tags you could wish for and even more! And that too in two easy steps! First of all, you have to enter a word and in the second step choose Technorati or some other seacrh engine and the tag for that site will be automatically generated..."
I was not specifically referring to Keotags. A google search produces many Technorati tag generators
(2) I have used tags and I have also chosen not to tag at all. The results were identical. Technorati and Google spiders pick up the key words and the categories from wordpress.com blogs easily.
Moreover, built in tagging on wordpress.com blogs is just around the corner so I wouldn't get too hyped about recommending 3rd party applications to wordpress.com bloggers as whatever you recommend now will soon be redundant.
(3) Technorati tag generators are features found in Windows Live Writer and in BlogDesk. The use of these off-line editors has many advantages including the back-up aspect of having a duplicate of every post made to your blog.
(4) The social bookmarks code being used for example on raincoaster's blog can be obtained from sunburntkamel's blog. http://archgfx.net/blog/2006/geek/blogging/social-bookmarks-on-wordpresscom
I'm not bothering to use it on my blog here right now. I will be using Alex King's on my wp.org install hosted elsewhere.
(5) I gave bloggersblurt to raincoaster weeks ago