ehabsan

This plugin enables you to easily add as many tags as you wish in one round, i tested it on my localhost to add 1000 tag and everything worked fine.
you can also specifiy a slug by using the following format tag,slug, a working example will be:
<pre><code>tag1
tag2,slug2
</code></pre>
When you don’t specifiy a slug the tag name will be used as the slug, so in the previous example 2 tags will be inserted tag1 with tag1 as the slug,and tag2 with slug2 as the slug
You can also edit a function that will be used to modifiy the tags you insert, if you wish to edit that function go to the directory where this plugin was installed and then to the admin directory, open the filter-tags.php file and edit that function.
You will see that function in this plugin’s settings page, however it will only be read-only so you can make sure that the tags will be modified as you expect them to be.

Quick Bulk Tags Creator

Easily add tags in bulk, and easily create a filter function to modifiy the values you insert

Birchdunford

Tags, tagging, and post tags made easy. Stop thinking about what tags you should add, forgetting to add certain tags, and typing in tags by hand. Let Tagbag do the work for you. Just look at the list of suggestions, click the ones you want, and move on. More on Tagbag: 
<a href="http://www.explodybits.com/2012/04/tagbag-wordpress-plugin/" title="explodybits (xb)" rel="nofollow ugc">explodybits (xb)</a>

Tagbag

Tagbag, takes the thought out of selecting tags for your post

Quick Bulk Tags Creator vs Tagbag