WordPress MU

hey there,
1st thing 1st xcuse my bad English.
am sorry if what is ask will sound silly (or maybe has been discussed somewhere in this forum or even has been solved!) but i cant find any solution for my problem.
i have a domain blog with 3 subdomain (this is my mini proj for uni)
now..i want to create "tags" from my domain blog, that can appear and be used by all my subdomains..how is this possible to be?is there any plugins that can make my work easier as i need to get the solution of this a.s.a.p...
huhu..
hope to get quick reply from anyone and pleaaaaaaaaseeee..give a good,working and easy to understand explaination/solution as am a noob xD thanks everyone!

let me make it clear..
" I want to create "tags" from my domain blog and it can appear and also can be used by all my sub-domain blog"
how to do it...pls helppppppppppp...=(

I'm not sure I understand your main blog/sub domain blog problem clearly, are you already using wpmu? if yes, then the site-wide-tags plugin is a great plugin to combine tags from many sub blogs to one main blog.
http://ocaoimh.ie/wordpress-mu-sitewide-tags/

I wrote a plugin that allows you to create categories across many blogs, and keep them updated, but it does not work for tags. (http://natureofmind.org/30/default-categories-for-new-blogs/)

hey dwenaus,
really much thanks for the quick reply.
yes i already use wp-mu.everythings ok so far. and i also has try mu-sitewide-tags plugin. it works for me, when everytime my subdomain create a tag,it will appear in my main blog.rite?

but my major probe now is, i want a plugin that will allow me to create any tags from my main blog, but can be view and USE by all my subdomain..huhu..i cant find any plugins yet for this probe...
i want to do this so that all my subdomain can just choose and reuse the tags i already create for them..is it possible, dwenaus?
pls help... =(