I've used WP Table in the past. The plug-in inserts tables via a shortcode, and is available in the WordPress plug-in repository.
Usually I write the content on windows live writer, then copy/paste the html content on WP. You can make table and all that in live writer.
Create the whole table in Adobe Dreamweaver or Microsoft FrontPage . Then just copy the table HTML code and paste it on your WordPress page/post as required. This is the easiest way to achieve this Good Luck
Use this plugin. Works out fine and have used for a few client sites too in the past. http://wordpress.org/extend/plugins/wp-table-reloaded/
There are few plugins available to create HTML tables in WordPress. WP Table Reloaded is the best of all. You may find this article helpful - http://wprockers.com/how-to-create-html-tables-in-wordpress-blog-post-easily-1100.html